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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group F. Templin, Ed. 3 Internet-Draft The Boeing Company 4 Updates: rfc1191, rfc4443, rfc8201 (if A. Whyman 5 approved) MWA Ltd c/o Inmarsat Global Ltd 6 Intended status: Standards Track January 26, 2021 7 Expires: July 30, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-70 13 Abstract 15 Mobile nodes (e.g., aircraft of various configurations, terrestrial 16 vehicles, seagoing vessels, enterprise wireless devices, etc.) 17 communicate with networked correspondents over multiple access 18 network data links and configure mobile routers to connect end user 19 networks. A multilink interface specification is therefore needed 20 for coordination with the network-based mobility service. This 21 document specifies the transmission of IP packets over Overlay 22 Multilink Network (OMNI) Interfaces. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on July 30, 2021. 41 Copyright Notice 43 Copyright (c) 2021 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 8 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 9 62 5. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 13 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 18 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 19 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 19 66 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 21 67 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 22 68 10. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 23 69 10.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 25 70 10.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 26 71 10.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 26 72 10.1.3. Interface Attributes . . . . . . . . . . . . . . . . 27 73 10.1.4. Traffic Selector . . . . . . . . . . . . . . . . . . 31 74 10.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . 31 75 10.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 32 76 10.1.7. Network Access Identifier (NAI) . . . . . . . . . . 32 77 10.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . 33 78 10.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . 33 79 10.1.10. DHCPv6 Message . . . . . . . . . . . . . . . . . . . 34 80 11. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 34 81 12. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 35 82 12.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 35 83 12.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 36 84 13. Router Discovery and Prefix Registration . . . . . . . . . . 36 85 13.1. Router Discovery in IP Multihop and IPv4-Only Networks . 40 86 13.2. MS-Register and MS-Release List Processing . . . . . . . 42 87 13.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 44 88 14. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 44 89 15. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 45 90 16. Detecting and Responding to MSE Failures . . . . . . . . . . 45 91 17. Transition Considerations . . . . . . . . . . . . . . . . . . 46 92 18. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 46 93 19. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 47 94 20. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 48 95 21. Security Considerations . . . . . . . . . . . . . . . . . . . 49 96 22. Implementation Status . . . . . . . . . . . . . . . . . . . . 49 97 23. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 50 98 24. References . . . . . . . . . . . . . . . . . . . . . . . . . 50 99 24.1. Normative References . . . . . . . . . . . . . . . . . . 50 100 24.2. Informative References . . . . . . . . . . . . . . . . . 52 101 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 58 102 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 60 103 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 61 104 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 61 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 64 107 1. Introduction 109 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 110 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 111 pedestrians with cellphones, etc.) often have multiple interface 112 connections to wireless and/or wired-link data links used for 113 communicating with networked correspondents. These data links may 114 have diverse performance, cost and availability properties that can 115 change dynamically according to mobility patterns, flight phases, 116 proximity to infrastructure, etc. MNs coordinate their data links in 117 a discipline known as "multilink", in which a single virtual 118 interface is configured over the node's underlying interface 119 connections to the data links. 121 The MN configures a virtual interface (termed the "Overlay Multilink 122 Network (OMNI) interface") as a thin layer over the underlying 123 interfaces. The OMNI interface is therefore the only interface 124 abstraction exposed to the IP layer and behaves according to the Non- 125 Broadcast, Multiple Access (NBMA) interface principle, while 126 underlying interfaces appear as link layer communication channels in 127 the architecture. The OMNI interface connects to a virtual overlay 128 service known as the "OMNI link". The OMNI link spans one or more 129 Internetworks that may include private-use infrastructures and/or the 130 global public Internet itself. 132 Each MN receives a Mobile Network Prefix (MNP) for numbering 133 downstream-attached End User Networks (EUNs) independently of the 134 access network data links selected for data transport. The MN 135 performs router discovery over the OMNI interface (i.e., similar to 136 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 137 behalf of its EUNs. The router discovery process is iterated over 138 each of the OMNI interface's underlying interfaces in order to 139 register per-link parameters (see Section 13). 141 The OMNI interface provides a multilink nexus for exchanging inbound 142 and outbound traffic via the correct underlying interface(s). The IP 143 layer sees the OMNI interface as a point of connection to the OMNI 144 link. Each OMNI link has one or more associated Mobility Service 145 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 146 prefixes from which OMNI link MNPs are derived. If there are 147 multiple OMNI links, the IPv6 layer will see multiple OMNI 148 interfaces. 150 MNs may connect to multiple distinct OMNI links by configuring 151 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 152 interface is configured over a set of underlying interfaces and 153 provides a nexus for Safety-Based Multilink (SBM) operation. Each 154 OMNI SBM "domain" configures a common ULA prefix [ULA]::/48, and each 155 OMNI link within the domain configures a unique 16-bit Subnet ID '*' 156 to construct the sub-prefix [ULA*]::/64 (see: Section 8). The IP 157 layer applies SBM routing to select an OMNI interface, which then 158 applies Performance-Based Multilink (PBM) to select the correct 159 underlying interface. Applications can apply Segment Routing 160 [RFC8402] to select independent SBM topologies for fault tolerance. 162 The OMNI interface interacts with a network-based Mobility Service 163 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 164 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 165 track MN movements and represent their MNPs in a global routing or 166 mapping system. 168 Many OMNI use cases are currently under active consideration. In 169 particular, the International Civil Aviation Organization (ICAO) 170 Working Group-I Mobility Subgroup is developing a future Aeronautical 171 Telecommunications Network with Internet Protocol Services (ATN/IPS) 172 and has issued a liaison statement requesting IETF adoption [ATN] in 173 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 174 in Vehicular Environments (ipwave) working group has further included 175 problem statement and use case analysis for OMNI in a document now in 176 AD evaluation for RFC publication 177 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 178 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 179 programs that examine commercial aviation, Urban Air Mobility (UAM) 180 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 181 represent another large class of potential OMNI users. 183 This document specifies the transmission of IP packets and MN/MS 184 control messages over OMNI interfaces. The OMNI interface supports 185 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 186 as the network layer in the data plane, while using IPv6 ND messaging 187 as the control plane independently of the data plane IP protocol(s). 188 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 189 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 190 discussed in the following sections. 192 2. Terminology 194 The terminology in the normative references applies; especially, the 195 terms "link" and "interface" are the same as defined in the IPv6 196 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 197 Additionally, this document assumes the following IPv6 ND message 198 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 199 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 201 The Protocol Constants defined in Section 10 of [RFC4861] are used in 202 their same format and meaning in this document. The terms "All- 203 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 204 are the same as defined in [RFC4291] (with Link-Local scope assumed). 206 The term "IP" is used to refer collectively to either Internet 207 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 208 specification at the layer in question applies equally to either 209 version. 211 The following terms are defined within the scope of this document: 213 Mobile Node (MN) 214 an end system with a mobile router having multiple distinct 215 upstream data link connections that are grouped together in one or 216 more logical units. The MN's data link connection parameters can 217 change over time due to, e.g., node mobility, link quality, etc. 218 The MN further connects a downstream-attached End User Network 219 (EUN). The term MN used here is distinct from uses in other 220 documents, and does not imply a particular mobility protocol. 222 End User Network (EUN) 223 a simple or complex downstream-attached mobile network that 224 travels with the MN as a single logical unit. The IP addresses 225 assigned to EUN devices remain stable even if the MN's upstream 226 data link connections change. 228 Mobility Service (MS) 229 a mobile routing service that tracks MN movements and ensures that 230 MNs remain continuously reachable even across mobility events. 231 Specific MS details are out of scope for this document. 233 Mobility Service Endpoint (MSE) 234 an entity in the MS (either singular or aggregate) that 235 coordinates the mobility events of one or more MN. 237 Mobility Service Prefix (MSP) 238 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 239 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 240 from which more-specific Mobile Network Prefixes (MNPs) are 241 delegated. OMNI link administrators typically obtain MSPs from an 242 Internet address registry, however private-use prefixes can 243 alternatively be used subject to certain limitations (see: 244 Section 9). OMNI links that connect to the global Internet 245 advertise their MSPs to their interdomain routing peers. 247 Mobile Network Prefix (MNP) 248 a longer IP prefix delegated from an MSP (e.g., 249 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 250 MNs sub-delegate the MNP to devices located in EUNs. 252 Access Network (ANET) 253 a data link service network (e.g., an aviation radio access 254 network, satellite service provider network, cellular operator 255 network, wifi network, etc.) that connects MNs. Physical and/or 256 data link level security is assumed, and sometimes referred to as 257 "protected spectrum". Private enterprise networks and ground 258 domain aviation service networks may provide multiple secured IP 259 hops between the MN's point of connection and the nearest Access 260 Router. 262 Access Router (AR) 263 a router in the ANET for connecting MNs to correspondents in 264 outside Internetworks. The AR may be located on the same physical 265 link as the MN, or may be located multiple IP hops away. In the 266 latter case, the MN uses encapsulation to communicate with the AR 267 as though it were on the same physical link. 269 ANET interface 270 a MN's attachment to a link in an ANET. 272 Internetwork (INET) 273 a connected network region with a coherent IP addressing plan that 274 provides transit forwarding services between ANETs and nodes that 275 connect directly to the open INET via unprotected media. No 276 physical and/or data link level security is assumed, therefore 277 security must be applied by upper layers. The global public 278 Internet itself is an example. 280 INET interface 281 a node's attachment to a link in an INET. 283 *NET 284 a "wildcard" term used when a given specification applies equally 285 to both ANET and INET cases. 287 OMNI link 288 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 289 over one or more INETs and their connected ANETs. An OMNI link 290 can comprise multiple INET segments joined by bridges the same as 291 for any link; the addressing plans in each segment may be mutually 292 exclusive and managed by different administrative entities. 294 OMNI interface 295 a node's attachment to an OMNI link, and configured over one or 296 more underlying *NET interfaces. If there are multiple OMNI links 297 in an OMNI domain, a separate OMNI interface is configured for 298 each link. 300 OMNI Adaptation Layer (OAL) 301 an OMNI interface process whereby packets admitted into the 302 interface are wrapped in a mid-layer IPv6 header and fragmented/ 303 reassembled if necessary to support the OMNI link Maximum 304 Transmission Unit (MTU). The OAL is also responsible for 305 generating MTU-related control messages as necessary, and for 306 providing addressing context for spanning multiple segments of a 307 bridged OMNI link. 309 OMNI Option 310 an IPv6 Neighbor Discovery option providing multilink parameters 311 for the OMNI interface as specified in Section 10. 313 Mobile Network Prefix Link Local Address (MNP-LLA) 314 an IPv6 Link Local Address that embeds the most significant 64 315 bits of an MNP in the lower 64 bits of fe80::/64, as specified in 316 Section 7. 318 Mobile Network Prefix Unique Local Address (MNP-ULA) 319 an IPv6 Unique-Local Address derived from an MNP-LLA. 321 Administrative Link Local Address (ADM-LLA) 322 an IPv6 Link Local Address that embeds a 32-bit administratively- 323 assigned identification value in the lower 32 bits of fe80::/96, 324 as specified in Section 7. 326 Administrative Unique Local Address (ADM-ULA) 327 an IPv6 Unique-Local Address derived from an ADM-LLA. 329 Multilink 330 an OMNI interface's manner of managing diverse underlying 331 interface connections to data links as a single logical unit. The 332 OMNI interface provides a single unified interface to upper 333 layers, while underlying interface selections are performed on a 334 per-packet basis considering factors such as DSCP, flow label, 335 application policy, signal quality, cost, etc. Multilinking 336 decisions are coordinated in both the outbound (i.e. MN to 337 correspondent) and inbound (i.e., correspondent to MN) directions. 339 L2 340 The second layer in the OSI network model. Also known as "layer- 341 2", "link-layer", "sub-IP layer", "data link layer", etc. 343 L3 344 The third layer in the OSI network model. Also known as "layer- 345 3", "network-layer", "IP layer", etc. 347 underlying interface 348 a *NET interface over which an OMNI interface is configured. The 349 OMNI interface is seen as a L3 interface by the IP layer, and each 350 underlying interface is seen as a L2 interface by the OMNI 351 interface. The underlying interface either connects directly to 352 the physical communications media or coordinates with another node 353 where the physical media is hosted. 355 Mobility Service Identification (MSID) 356 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 357 (see: Section 7). IDs are assigned according to MS-specific 358 guidelines (e.g., see: [I-D.templin-intarea-6706bis]). 360 Safety-Based Multilink (SBM) 361 A means for ensuring fault tolerance through redundancy by 362 connecting multiple affiliated OMNI interfaces to independent 363 routing topologies (i.e., multiple independent OMNI links). 365 Performance Based Multilink (PBM) 366 A means for selecting underlying interface(s) for packet 367 transmission and reception within a single OMNI interface. 369 OMNI Domain 370 The set of all SBM/PBM OMNI links that collectively provides 371 services for a common set of MSPs. Each OMNI domain consists of a 372 set of affiliated OMNI links that all configure the same ::/48 ULA 373 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 375 3. Requirements 377 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 378 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 379 "OPTIONAL" in this document are to be interpreted as described in BCP 380 14 [RFC2119][RFC8174] when, and only when, they appear in all 381 capitals, as shown here. 383 OMNI links maintain a constant value "MAX_MSID" selected to provide 384 MNs with an acceptable level of MSE redundancy while minimizing 385 control message amplification. It is RECOMMENDED that MAX_MSID be 386 set to the default value 5; if a different value is chosen, it should 387 be set uniformly by all nodes on the OMNI link. 389 An implementation is not required to internally use the architectural 390 constructs described here so long as its external behavior is 391 consistent with that described in this document. 393 4. Overlay Multilink Network (OMNI) Interface Model 395 An OMNI interface is a MN virtual interface configured over one or 396 more underlying interfaces, which may be physical (e.g., an 397 aeronautical radio link) or virtual (e.g., an Internet or higher- 398 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 399 with the MS through IPv6 ND message exchanges. The MN uses the MNP 400 to construct a unique Link-Local Address (MNP-LLA) through the 401 algorithmic derivation specified in Section 7 and assigns the LLA to 402 the OMNI interface. 404 The OMNI interface architectural layering model is the same as in 405 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 406 therefore sees the OMNI interface as a single L3 interface with 407 multiple underlying interfaces that appear as L2 communication 408 channels in the architecture. 410 +----------------------------+ 411 | Upper Layer Protocol | 412 Session-to-IP +---->| | 413 Address Binding | +----------------------------+ 414 +---->| IP (L3) | 415 IP Address +---->| | 416 Binding | +----------------------------+ 417 +---->| OMNI Interface | 418 Logical-to- +---->| (LLA) | 419 Physical | +----------------------------+ 420 Interface +---->| L2 | L2 | | L2 | 421 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 422 +------+------+ +------+ 423 | L1 | L1 | | L1 | 424 | | | | | 425 +------+------+ +------+ 427 Figure 1: OMNI Interface Architectural Layering Model 429 Each underlying interface provides an L2/L1 abstraction according to 430 one of the following models: 432 o INET interfaces connect to an INET either natively or through one 433 or several IPv4 Network Address Translators (NATs). Native INET 434 interfaces have global IP addresses that are reachable from any 435 INET correspondent. NATed INET interfaces typically have private 436 IP addresses and connect to a private network behind one or more 437 NATs that provide INET access. 439 o ANET interfaces connect to a protected ANET that is separated from 440 the open INET by an AR acting as a proxy. The ANET interface may 441 be either on the same L2 link segment as the AR, or separated from 442 the AR by multiple IP hops. 444 o VPNed interfaces use security encapsulation over a *NET to a 445 Virtual Private Network (VPN) gateway. Other than the link-layer 446 encapsulation format, VPNed interfaces behave the same as for 447 Direct interfaces. 449 o Direct (aka "point-to-point") interfaces connect directly to a 450 peer without crossing any *NET paths. An example is a line-of- 451 sight link between a remote pilot and an unmanned aircraft. 453 The OMNI virtual interface model gives rise to a number of 454 opportunities: 456 o since MNP-LLAs are uniquely derived from an MNP, no Duplicate 457 Address Detection (DAD) or Multicast Listener Discovery (MLD) 458 messaging is necessary. 460 o since Temporary LLAs are statistically unique, they can be used 461 without DAD for short-term purposes, e.g. until an MNP-LLA is 462 obtained. 464 o *NET interfaces on the same L2 link segment as an AR do not 465 require any L3 addresses (i.e., not even link-local) in 466 environments where communications are coordinated entirely over 467 the OMNI interface. (An alternative would be to also assign the 468 same LLA to all *NET interfaces.) 470 o as underlying interface properties change (e.g., link quality, 471 cost, availability, etc.), any active interface can be used to 472 update the profiles of multiple additional interfaces in a single 473 message. This allows for timely adaptation and service continuity 474 under dynamically changing conditions. 476 o coordinating underlying interfaces in this way allows them to be 477 represented in a unified MS profile with provisions for mobility 478 and multilink operations. 480 o exposing a single virtual interface abstraction to the IPv6 layer 481 allows for multilink operation (including QoS based link 482 selection, packet replication, load balancing, etc.) at L2 while 483 still permitting L3 traffic shaping based on, e.g., DSCP, flow 484 label, etc. 486 o the OMNI interface allows inter-INET traversal when nodes located 487 in different INETs need to communicate with one another. This 488 mode of operation would not be possible via direct communications 489 over the underlying interfaces themselves. 491 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 492 lossless and adaptive path MTU mitigations not available for 493 communications directly over the underlying interfaces themselves. 495 o L3 sees the OMNI interface as a point of connection to the OMNI 496 link; if there are multiple OMNI links (i.e., multiple MS's), L3 497 will see multiple OMNI interfaces. 499 o Multiple independent OMNI interfaces can be used for increased 500 fault tolerance through Safety-Based Multilink (SBM), with 501 Performance-Based Multilink (PBM) applied within each interface. 503 Other opportunities are discussed in [RFC7847]. Note that even when 504 the OMNI virtual interface is present, applications can still access 505 underlying interfaces either through the network protocol stack using 506 an Internet socket or directly using a raw socket. This allows for 507 intra-network (or point-to-point) communications without invoking the 508 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 509 is configured over an underlying IPv4 interface, applications can 510 still invoke IPv4 intra-network communications as long as the 511 communicating endpoints are not subject to mobility dynamics. 512 However, the opportunities discussed above are not available when the 513 architectural layering is bypassed in this way. 515 Figure 2 depicts the architectural model for a MN with an attached 516 EUN connecting to the MS via multiple independent *NETs. When an 517 underlying interface becomes active, the MN's OMNI interface sends 518 IPv6 ND messages without encapsulation if the first-hop Access Router 519 (AR) is on the same underlying link; otherwise, the interface uses 520 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 521 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 522 then coordinates with an INET Mobility Service Endpoint (MSE#1, 523 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 524 The Hop Limit in IPv6 ND messages is not decremented due to 525 encapsulation; hence, the OMNI interface appears to be attached to an 526 ordinary link. 528 +--------------+ (:::)-. 529 | MN |<-->.-(::EUN:::) 530 +--------------+ `-(::::)-' 531 |OMNI interface| 532 +----+----+----+ 533 +--------|IF#1|IF#2|IF#n|------ + 534 / +----+----+----+ \ 535 / | \ 536 / | \ 537 v v v 538 (:::)-. (:::)-. (:::)-. 539 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 540 `-(::::)-' `-(::::)-' `-(::::)-' 541 +----+ +----+ +----+ 542 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 543 . +-|--+ +-|--+ +-|--+ . 544 . | | | 545 . v v v . 546 . <----- INET Encapsulation -----> . 547 . . 548 . +-----+ (:::)-. . 549 . |MSE#2| .-(::::::::) +-----+ . 550 . +-----+ .-(::: INET :::)-. |MSE#m| . 551 . (::::: Routing ::::) +-----+ . 552 . `-(::: System :::)-' . 553 . +-----+ `-(:::::::-' . 554 . |MSE#1| +-----+ +-----+ . 555 . +-----+ |MSE#3| |MSE#4| . 556 . +-----+ +-----+ . 557 . . 558 . . 559 . <----- Worldwide Connected Internetwork ----> . 560 ........................................................... 562 Figure 2: MN/MS Coordination via Multiple *NETs 564 After the initial IPv6 ND message exchange, the MN (and/or any nodes 565 on its attached EUNs) can send and receive IP data packets over the 566 OMNI interface. OMNI interface multilink services will forward the 567 packets via ARs in the correct underlying *NETs. The AR encapsulates 568 the packets according to the capabilities provided by the MS and 569 forwards them to the next hop within the worldwide connected 570 Internetwork via optimal routes. 572 OMNI links span one or more underlying Internetwork via the OMNI 573 Adaptation Layer (OAL) which is based on a mid-layer overlay 574 encapsulation using [RFC2473]. Each OMNI link corresponds to a 575 different overlay (differentiated by an address codepoint) which may 576 be carried over a completely separate underlying topology. Each MN 577 can facilitate SBM by connecting to multiple OMNI links using a 578 distinct OMNI interface for each link. 580 Note: OMNI interface underlying interfaces often connect directly to 581 physical media on the local platform (e.g., a laptop computer with 582 WiFi, etc.), but in some configurations the physical media may be 583 hosted on a separate Local Area Network (LAN) node. In that case, 584 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 585 tunnel (at a layer below the underlying interface) to the node 586 hosting the physical media. The OMNI interface may also apply 587 encapsulation at a layer above the underlying interface such that 588 packets would appear "double-encapsulated" on the LAN; the node 589 hosting the physical media in turn removes the LAN encapsulation 590 prior to transmission or inserts it following reception. Finally, 591 the underlying interface must monitor the node hosting the physical 592 media (e.g., through periodic keepalives) so that it can convey 593 up/down/status information to the OMNI interface. 595 5. The OMNI Adaptation Layer (OAL) 597 The OMNI interface observes the link nature of tunnels, including the 598 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 599 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 600 The OMNI interface is configured over one or more underlying 601 interfaces that may have diverse MTUs. OMNI interfaces accommodate 602 MTU diversity through the use of the OMNI Adaptation Layer (OAL) as 603 discussed in this section. 605 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 606 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 607 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 608 permitted to perform network fragmentation even though the 609 destination is required to reassemble more. The network therefore 610 MUST forward packets of at least 1280 bytes without generating an 611 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 612 [RFC8201]. (Note: the source can apply "source fragmentation" for 613 locally-generated IPv6 packets up to 1500 bytes and larger still if 614 it if has a way to determine that the destination configures a larger 615 MRU, but this does not affect the minimum IPv6 path MTU.) 617 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 618 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 619 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 620 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 621 support network fragmentation and the destination is required to 622 reassemble at least that much. The "Don't Fragment" (DF) bit in the 623 IPv4 encapsulation headers of packets sent over IPv4 underlying 624 interfaces therefore MUST be set to 0. (Note: even if the 625 encapsulation source has a way to determine that the encapsulation 626 destination configures an MRU larger than 576 bytes, it should not 627 assume a larger minimum IPv4 path MTU without careful consideration 628 of the issues discussed in Section 5.1.) 630 In network paths where IPv6/IPv4 protocol translation or IPv6-in-IPv4 631 encapsulation may be prevalent, it may be prudent for the OAL to 632 always assume the IPv4 minimum path MTU (i.e., 576 bytes) regardless 633 of the underlying interface IP protocol version. Always assuming the 634 IPv4 minimum path MTU even for IPv6 underlying interfaces may produce 635 more fragments and additional header overhead, but will always 636 interoperate and never run the risk of presenting an IPv4 interface 637 with a packet that exceeds its MRU. 639 The OMNI interface configures both an MTU and MRU of 9180 bytes 640 [RFC2492]; the size is therefore not a reflection of the underlying 641 interface MTUs, but rather determines the largest packet the OMNI 642 interface can forward or reassemble. The OMNI interface uses the 643 OMNI Adaptation Layer (OAL) to admit packets from the network layer 644 that are no larger than the OMNI interface MTU while generating 645 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 646 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 647 document refers to both of these ICMPv4/ICMPv6 message types simply 648 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 649 errors as discussed below. 651 For IPv4 packets with DF=0, the network layer performs IPv4 652 fragmentation if necessary then admits the packets/fragments into the 653 OMNI interface; these fragments will be reassembled by the final 654 destination. For IPv4 packets with DF=1 and IPv6 packets, the 655 network layer admits the packet if it is no larger than the OMNI 656 interface MTU; otherwise, it drops the packet and returns a PTB hard 657 error message to the source. 659 For each admitted IP packet/fragment, the OMNI interface internally 660 employs the OAL when necessary by encapsulating the inner IP packet/ 661 fragment in a mid-layer IPv6 header per [RFC2473] before adding any 662 outer IP encapsulations. (The OAL does not decrement the inner IP 663 Hop Limit/TTL during encapsulation since the insertion occurs at a 664 layer below IP forwarding.) The OAL then calculates the 32-bit CRC 665 over the entire mid-layer packet and writes the value in a trailing 666 4-octet field at the end of the packet. Next, the OAL fragments this 667 mid-layer IPv6 packet, forwards the fragments (using *NET 668 encapsulation if necessary), and returns an internally-generated PTB 669 soft error message (subject to rate limiting) if it deems the packet 670 too large according to factors such as link performance 671 characteristics, reassembly congestion, etc. This ensures that the 672 path MTU is adaptive and reflects the current path used for a given 673 data flow. 675 The OAL operates with respect to both the minimum IPv6 and IPv4 path 676 MTUs as follows: 678 o When an OMNI interface sends a packet toward a final destination 679 via an ANET peer, it sends without OAL encapsulation if the packet 680 (including any outer-layer ANET encapsulations) is no larger than 681 the underlying interface MTU for on-link ANET peers or the minimum 682 ANET path MTU for peers separated by multiple IP hops. Otherwise, 683 the OAL inserts an IPv6 header per [RFC2473] with source address 684 set to the node's own Unique-Local Address (ULA) (see: Section 8) 685 and destination set to either the Administrative ULA (ADM-ULA) of 686 the ANET peer or the Mobile Network Prefix ULA (MNP-ULA) 687 corresponding to the final destination (see below). The OAL then 688 calculates and appends the trailing 32-bit CRC, then uses IPv6 689 fragmentation to break the packet into a minimum number of non- 690 overlapping fragments where the size of each non-final fragment 691 (including both the OMNI and any outer-layer ANET encapsulations) 692 is determined by the underlying interface MTU for on-link ANET 693 peers or the minimum ANET path MTU for peers separated by multiple 694 IP hops. The OAL then encapsulates the fragments in any ANET 695 headers and sends them to the ANET peer, which either reassembles 696 before forwarding if the OAL destination is its own ADM-ULA or 697 forwards the fragments toward the final destination without first 698 reassembling otherwise. 700 o When an OMNI interface sends a packet toward a final destination 701 via an INET interface, it sends packets (including any outer-layer 702 INET encapsulations) no larger than the minimum INET path MTU 703 without OAL encapsulation if the destination is reached via an 704 INET address within the same OMNI link segment. Otherwise, the 705 OAL inserts an IPv6 header per [RFC2473] with source address set 706 to the node's ULA, destination set to the ULA of the next hop OMNI 707 node toward the final destination and (if necessary) with an OMNI 708 Routing Header (ORH) (see: [I-D.templin-intarea-6706bis]) with 709 final segment addressing information. The OAL then calculates and 710 appends the trailing 32-bit CRC, then uses IPv6 fragmentation to 711 break the packet into a minimum number of non-overlapping 712 fragments where the size of each non-final fragment (including 713 both the OMNI and outer-layer INET encapsulations) is determined 714 by the minimum INET path MTU. The OAL then encapsulates the 715 fragments in any INET headers and sends them to the OMNI link 716 neighbor, which reassembles before forwarding toward the final 717 destination. 719 In light of the above considerations, the OAL should assume a minimum 720 path MTU of 576 bytes for the purpose of generating OAL fragments. 721 Each OAL fragment will undergo *NET encapsulation including either a 722 20 byte IPv4 or 40 byte IPv6 header plus an 8 byte UDP header, 723 leaving a minimum of 528 bytes for each fragment. Each OAL fragment 724 must accommodate 48 bytes for the OAL IPv6 header plus fragment 725 header, with the remaining space available for a portion of the inner 726 IP packet while reserving 40 additional bytes in case a maximum- 727 length ORH is added due to re-encapsulation. OAL fragmentation 728 algorithms must therefore produce non-final fragments that are 488 729 bytes in length (i.e., not including the ORH length), while the final 730 fragment may be smaller. OAL fragmentation algorithms may produce 731 larger non-final fragments if better path MTU information is 732 available, but must not produce smaller non-final fragments. 734 Note that when two ANET peers share a common physical or virtual link 735 with a larger MTU such as 1500 bytes or larger, OAL fragmentation may 736 use this larger MTU size as long as the receiving ANET peer 737 reassembles (and possibly also refragments) before forwarding. This 738 is important for accommodating links where performance is highly 739 dependent on maximum use of the available link MTU, e.g. for wireless 740 aviation data links. Additionally, in order to set the correct 741 context for reassembly, the OMNI interface that inserts the OAL 742 header MUST also be the one that inserts the IPv6 fragment header 743 Identification value. While not strictly required, sending all 744 fragments of the same fragmented OAL packet consecutively over the 745 same underlying interface with minimal inter-fragment delay may 746 increase the likelihood of successful reassembly. 748 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 749 header Code field value 0 are hard errors that always indicate that a 750 packet has been dropped due to a real MTU restriction. However, the 751 OAL can also forward large packets via encapsulation and 752 fragmentation while at the same time returning PTB soft error 753 messages (subject to rate limiting) indicating that a forwarded 754 packet was uncomfortably large. The OMNI interface can therefore 755 continuously forward large packets without loss while returning PTB 756 soft error messages recommending a smaller size. Original sources 757 that receive the soft errors in turn reduce the size of the packets 758 they send, i.e., the same as for hard errors. 760 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 761 field to the value 1 in PTB soft error messages. The OAL sets the 762 PTB destination address to the source address of the original packet, 763 and sets the source address to the MNP Subnet Router Anycast address 764 of the MN (i.e., whether the MN was the source or target of the 765 original packet). The OAL then sets the MTU field to a value no 766 smaller than 576 for ICMPv4 or 1280 for ICMPv6, and returns the PTB 767 soft error to the original source. 769 When the original source receives the PTB, it reduces its path MTU 770 estimate the same as for hard errors but does not regard the message 771 as a loss indication. (If the original source does not recognize the 772 soft error code, it regards the PTB the same as a hard error but 773 should heed the retransmission advice given in [RFC8201] suggesting 774 retransmission based on normal packetization layer retransmission 775 timers.) This document therefore updates [RFC1191][RFC4443] and 776 [RFC8201]. Furthermore, implementations of [RFC4821] must be aware 777 that PTB hard or soft errors may arrive at any time even if after a 778 successful MTU probe (this is the same consideration as for an 779 ordinary path fluctuation following a successful probe). 781 In summary, the OAL supports continuous transmission and reception of 782 packets of various sizes in the face of dynamically changing network 783 conditions. Moreover, since PTB soft errors do not indicate loss, 784 original sources that receive soft errors can quickly scan for path 785 MTU increases without waiting for the minimum 10 minutes specified 786 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 787 therefore provides a lossless and adaptive service that accommodates 788 MTU diversity especially well-suited for dynamic multilink 789 environments. 791 Note: An OMNI interface that reassembles OAL fragments may experience 792 congestion-oriented loss in its reassembly cache and can optionally 793 send PTB soft errors to the original source and/or ICMP "Time 794 Exceeded" messages to the source of the OAL fragments. In 795 environments where the messages may contribute to unacceptable 796 additional congestion, however, the OMNI interface can simply regard 797 the loss as an ordinary unreported congestion event for which the 798 original source will eventually compensate. 800 Note: When the network layer forwards an IPv4 packet/fragment with 801 DF=0 into the OMNI interface, the interface can optionally perform 802 (further) IPv4 fragmentation before invoking the OAL so that the 803 fragments will be reassembled by the final destination. When the 804 network layer performs IPv6 fragmentation for locally-generated IPv6 805 packets, the OMNI interface typically invokes the OAL without first 806 applying (further) IPv6 fragmentation; the network layer should 807 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 808 push the reassembly burden to the final destination and avoid 809 receiving PTB soft errors from the OMNI interface. Aside from these 810 non-normative guidelines, the manner in which any IP fragmentation is 811 invoked prior to OAL encapsulation/fragmentation is an implementation 812 matter. 814 Note: Inclusion of the 32-bit CRC prior to fragmentation assumes that 815 the receiving OAL will discard any packets with incorrect CRC values 816 following reassembly. The 32-bit CRC is sufficient to detect 817 reassembly misassociations for packet sizes up to the OMNI interface 818 MTU 9180 but may not be sufficient to detect errors for larger sizes 819 [CRC]. 821 Note: Some underlying interface types (e.g., VPNs) may already 822 provide their own robust fragmentation and reassembly services even 823 without OAL encapsulation. In those cases, the OAL can invoke the 824 inherent underlying interface schemes instead while employing PTB 825 soft errors in the same fashion as described above. Other underlying 826 interface properties such as header/message compression can also be 827 harnessed in a similar fashion. 829 Note: Applications can dynamically tune the size of the packets they 830 to send to produce the best possible throughput and latency, with the 831 understanding that these parameters may change over time due to 832 factors such as congestion, mobility, network path changes, etc. The 833 receipt or absence of soft errors should be seen as hints of when 834 increasing or decreasing packet sizes may be beneficial. 836 5.1. Fragmentation Security Implications 838 As discussed in Section 3.7 of [RFC8900], there are four basic 839 threats concerning IPv6 fragmentation; each of which is addressed by 840 effective mitigations as follows: 842 1. Overlapping fragment attacks - reassembly of overlapping 843 fragments is forbidden by [RFC8200]; therefore, this threat does 844 not apply to the OAL. 846 2. Resource exhaustion attacks - this threat is mitigated by 847 providing a sufficiently large OAL reassembly cache and 848 instituting "fast discard" of incomplete reassemblies that may be 849 part of a buffer exhaustion attack. The reassembly cache should 850 be sufficiently large so that a sustained attack does not cause 851 excessive loss of good reassemblies but not so large that (timer- 852 based) data structure management becomes computationally 853 expensive. The cache should also be indexed based on the arrival 854 underlying interface such that congestion experienced over a 855 first underlying interface does not cause discard of incomplete 856 reassemblies for uncongested underlying interfaces. 858 3. Attacks based on predictable fragment identification values - 859 this threat is mitigated by selecting a suitably random ID value 860 per [RFC7739]. 862 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 863 threat is mitigated by disallowing "tiny fragments" per the OAL 864 fragmentation procedures specified above. 866 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 867 ID) field with only 65535 unique values such that at high data rates 868 the field could wrap and apply to new packets while the fragments of 869 old packets using the same ID are still alive in the network 870 [RFC4963]. However, since the largest OAL fragment that will be sent 871 via an IPv4 *NET path is 576 bytes any IPv4 fragmentation would occur 872 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 873 recommendations suggest that such links will have low data rates. 874 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 875 at high data rates is not a concern for IPv6 fragmentation. 877 Finally, [RFC6980] documents fragmentation security concerns for 878 large IPv6 ND messages. These concerns are addressed when OAL 879 segmentation and reassembly are used instead of direct fragmentation 880 of the IPv6 ND message itself. 882 6. Frame Format 884 The OMNI interface transmits IPv6 packets according to the native 885 frame format of each underlying interface. For example, for 886 Ethernet-compatible interfaces the frame format is specified in 887 [RFC2464], for aeronautical radio interfaces the frame format is 888 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 889 Manual), for tunnels over IPv6 the frame format is specified in 890 [RFC2473], etc. 892 7. Link-Local Addresses (LLAs) 894 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 895 (LLAs) through pre-service administrative actions. "MNP-LLAs" embed 896 the MNP assigned to the mobile node, while "ADM-LLAs" include an 897 administratively-unique ID that is guaranteed to be unique on the 898 link. LLAs are configured as follows: 900 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 901 the least-significant 64 bits of the IPv6 link-local prefix 902 fe80::/64, i.e., in the LLA "interface identifier" portion. The 903 prefix length for the LLA is determined by adding 64 to the MNP 904 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 905 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 907 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 908 i.e., the interface identifier consists of 16 '0' bits, followed 909 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 910 prefix length for the LLA is determined by adding 96 to the MNP 911 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 912 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 913 fe80::ffff:c000:0200/120). 915 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 916 uniqueness. The lower 32 bits of the LLA includes a unique 917 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 918 in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA 919 prefix length is determined by adding 96 to the MSID prefix 920 length. For example, if the prefix length for MSID 0x10012001 is 921 16 then the ADM-LLA prefix length is set to 112 and the LLA is 922 written as fe80::1001:2001/112. The "zero" address for each ADM- 923 LLA prefix is the Subnet-Router anycast address for that prefix 924 [RFC4291]; for example, the Subnet-Router anycast address for 925 fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range 926 0xff000000 through 0xffffffff is reserved for future use. 928 o Temporary LLAs are constructed per [I-D.ietf-6man-rfc4941bis] and 929 used by MNs for the short-term purpose of procuring an actual MNP- 930 LLA upon startup or (re)connecting to the network. MNs may use 931 Temporary LLAs as the IPv6 source address of an RS message in 932 order to request a MNP-LLA from the MS. 934 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 935 MNPs can be allocated from that block ensuring that there is no 936 possibility for overlap between the various LLA constructs discussed 937 above. 939 Since MNP-LLAs are based on the distribution of administratively 940 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 941 administrative assignment, OMNI interfaces set the autoconfiguration 942 variable DupAddrDetectTransmits to 0 [RFC4862]. 944 Temporary LLAs employ optimistic DAD principles [RFC4429] since they 945 are probabilistically unique and their use is short-duration in 946 nature. 948 Note: If future protocol extensions relax the 64-bit boundary in IPv6 949 addressing, the additional prefix bits of an MNP could be encoded in 950 bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits 951 would therefore still be in bits 64-127, and the remaining bits would 952 appear in bits 16 through 48.) However, the analysis provided in 953 [RFC7421] suggests that the 64-bit boundary will remain in the IPv6 954 architecture for the forseeable future. 956 Note: Even though this document honors the 64-bit boundary in IPv6 957 addressing per [RFC7421], it suggests prefix lengths longer than /64 958 for routing purposes. This effectively extends IPv6 routing 959 determination into the interface identifier portion of the IPv6 960 address, but it does not redefine the 64-bit boundary. 962 8. Unique-Local Addresses (ULAs) 964 OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and 965 destination addresses in OAL IPv6 encapsulation headers. ULAs are 966 only routable within the scope of a an OMNI domain, and are derived 967 from the IPv6 Unique Local Address prefix fc00::/7 followed by the L 968 bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo-random 969 Global ID to produce the prefix [ULA]::/48, which is then followed by 970 a 16-bit Subnet ID then finally followed by a 64 bit Interface ID as 971 specified in Section 3 of [RFC4193]. The statistic uniqueness of the 972 40-bit pseudo-random Global ID allows different OMNI domains to be 973 joined together in the future without requiring OMNI link 974 renumbering. 976 Each OMNI link instance is identified by a value between 0x0000 and 977 0xfeff in bits 48-63 of [ULA]::/48 (the values 0xff00 through 0xffff 978 are reserved for future use). For example, OMNI ULAs associated with 979 instance 0 are configured from the prefix [ULA]:0000::/64, instance 1 980 from [ULA]:0001::/64, instance 2 from [ULA]:0002::/64, etc. ULAs and 981 their associated prefix lengths are configured in correspondence with 982 LLAs through stateless prefix translation where "MNP-ULAs" are 983 assigned in correspondence to MNP-LLAs and "ADM-ULAs" are assigned in 984 correspondence to ADM-LLAs. For example, for OMNI link instance 985 [ULA]:1010::/64: 987 o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 988 56-bit MNP length is derived by copying the lower 64 bits of the 989 LLA into the lower 64 bits of the ULA as 990 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 991 64 plus the IPv6 MNP length). 993 o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 994 MNP length is derived by simply writing the LLA interface ID into 995 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 996 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 998 o the ADM-ULA corresponding to fe80::1000/112 is simply 999 [ULA]:1010::1000/112. 1001 o the ADM-ULA corresponding to fe80::/128 is simply 1002 [ULA]:1010::/128. 1004 o the Temporary ULA corresponding to a Temporary LLA is simply 1005 [ULA]:1010:[64-bit Temporary Interface ID]/128. 1007 o etc. 1009 Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI 1010 link instance. For example, the OMNI interface connected to instance 1011 3 assigns the Anycast address [ULA]:0003::/128. Routers that 1012 configure OMNI interfaces advertise the OMNI service prefix (e.g., 1013 [ULA]:0003::/64) into the local routing system so that applications 1014 can direct traffic according to SBM requirements. 1016 The ULA presents an IPv6 address format that is routable within the 1017 OMNI routing system and can be used to convey link-scoped IPv6 ND 1018 messages across multiple hops using IPv6 encapsulation [RFC2473]. 1019 The OMNI link extends across one or more underling Internetworks to 1020 include all ARs and MSEs. All MNs are also considered to be 1021 connected to the OMNI link, however OAL encapsulation is omitted 1022 whenever possible to conserve bandwidth (see: Section 12). 1024 Each OMNI link can be subdivided into "segments" that often 1025 correspond to different administrative domains or physical 1026 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 1027 necessary to support efficient packet forwarding to destinations 1028 located in other OMNI link segments. A full discussion of Segment 1029 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 1031 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 1032 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 1033 however the range could be used for MSP and MNP addressing under 1034 certain limiting conditions (see: Section 9). 1036 9. Global Unicast Addresses (GUAs) 1038 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 1039 as Mobility Service Prefixes (MSPs) from which Mobile Network 1040 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 1042 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 1043 associated regional assigned numbers authority such that the OMNI 1044 domain can be interconnected to the global IPv6 Internet without 1045 causing inconsistencies in the routing system. An OMNI domain could 1046 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 1047 fc00::/8)[RFC4193], however this would require IPv6 NAT if the domain 1048 were ever connected to the global IPv6 Internet. 1050 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 1051 associated regional assigned numbers authority such that the OMNI 1052 domain can be interconnected to the global IPv4 Internet without 1053 causing routing inconsistencies. An OMNI domain could instead use 1054 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1055 this would require IPv4 NAT if the domain were ever connected to the 1056 global IPv4 Internet. 1058 10. Address Mapping - Unicast 1060 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1061 state and use the link-local address format specified in Section 7. 1062 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1063 over physical underlying interfaces without encapsulation observe the 1064 native underlying interface Source/Target Link-Layer Address Option 1065 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1066 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1067 interfaces via encapsulation do not include S/TLLAOs which were 1068 intended for encoding physical L2 media address formats and not 1069 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1070 for encoding additional interface attributes needed for multilink 1071 coordination. Hence, this document does not define an S/TLLAO format 1072 but instead defines a new option type termed the "OMNI option" 1073 designed for these purposes. 1075 MNs such as aircraft typically have many wireless data link types 1076 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1077 etc.) with diverse performance, cost and availability properties. 1078 The OMNI interface would therefore appear to have multiple L2 1079 connections, and may include information for multiple underlying 1080 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1081 an IPv6 ND option called the OMNI option formatted as shown in 1082 Figure 3: 1084 0 1 2 3 1085 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1086 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1087 | Type | Length |T| Preflen | S/T-ifIndex | 1088 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1089 | | 1090 ~ Sub-Options ~ 1091 | | 1092 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1094 Figure 3: OMNI Option Format 1096 In this format: 1098 o Type is set to TBD. 1100 o Length is set to the number of 8 octet blocks in the option. 1102 o T is a 1-bit flag set to 1 for Temporary LLAs (otherwise, set to 1103 0) and Preflen is a 7 bit field that determines the length of 1104 prefix associated with an LLA. Values 1 through 127 specify a 1105 prefix length, while the value 0 indicates "unspecified". For 1106 IPv6 ND messages sent from a MN to the MS, T and Preflen apply to 1107 the IPv6 source LLA and provide the length that the MN is 1108 requesting or asserting to the MS. For IPv6 ND messages sent from 1109 the MS to the MN, T and Preflen apply to the IPv6 destination LLA 1110 and indicate the length that the MS is granting to the MN. For 1111 IPv6 ND messages sent between MS endpoints, T is set to 0 and 1112 Preflen provides the length associated with the source/target MN 1113 that is subject of the ND message. 1115 o S/T-ifIndex corresponds to the ifIndex value for source or target 1116 underlying interface used to convey this IPv6 ND message. OMNI 1117 interfaces MUST number each distinct underlying interface with an 1118 ifIndex value between '1' and '255' that represents a MN-specific 1119 8-bit mapping for the actual ifIndex value assigned by network 1120 management [RFC2863] (the ifIndex value '0' is reserved for use by 1121 the MS). For RS and NS messages, S/T-ifIndex corresponds to the 1122 source underlying interface the message originated from. For RA 1123 and NA messages, S/T-ifIndex corresponds to the target underlying 1124 interface that the message is destined to. (For NS messages used 1125 for Neighbor Unreachability Detection (NUD), S/T-ifIndex instead 1126 identifies the neighbor's underlying interface to be used as the 1127 target interface to return the NA.) 1129 o Sub-Options is a Variable-length field, of length such that the 1130 complete OMNI Option is an integer multiple of 8 octets long. 1131 Contains one or more Sub-Options, as described in Section 10.1. 1133 The OMNI option may appear in any IPv6 ND message type; it is 1134 processed by interfaces that recognize the option and ignored by all 1135 other interfaces. If multiple OMNI option instances appear in the 1136 same IPv6 ND message, the interface processes the T, Preflen and S/ 1137 T-ifIndex fields in the first instance and ignores those fields in 1138 all other instances. The interface processes the Sub-Options of all 1139 OMNI option instances in the consecutive order in which they appear 1140 in the IPv6 ND message, beginning with the first instance and 1141 continuing consecutively through any additional instances to the end 1142 of the message. 1144 The OMNI option(s) in each IPv6 ND message may include full or 1145 partial information for the neighbor. The union of the information 1146 in the most recently received OMNI options is therefore retained, and 1147 the information is aged/removed in conjunction with the corresponding 1148 neighbor cache entry. 1150 10.1. Sub-Options 1152 The OMNI option includes zero or more Sub-Options. Each consecutive 1153 Sub-Option is concatenated immediately after its predecessor. All 1154 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1155 encoded in the following format: 1157 0 1 2 1158 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 1159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1160 | Sub-Type | Sub-length | Sub-Option Data ... 1161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1163 Figure 4: Sub-Option Format 1165 o Sub-Type is a 6-bit field that encodes the Sub-Option type. Sub- 1166 Options defined in this document are: 1168 Option Name Sub-Type 1169 Pad1 0 1170 PadN 1 1171 Interface Attributes 2 1172 Traffic Selector 3 1173 MS-Register 4 1174 MS-Release 5 1175 Network Access Identifier 6 1176 Geo Coordinates 7 1177 DHCP Unique Identifier (DUID) 8 1178 DHCPv6 Message 9 1180 Figure 5 1182 Sub-Types 10-61 are available for future assignment. Sub-Type 62 1183 is reserved for experimentation, as recommended in [RFC3692]. 1184 Sub-Type 63 is reserved by IANA. 1186 o Sub-Length is a 10-bit field that encodes the length of the Sub- 1187 Option Data (i.e., ranging from 0 to 1023 octets). 1189 o Sub-Option Data is a block of data with format determined by Sub- 1190 Type and length determined by Sub-Length. 1192 Note that Sub-Type and Sub-Length are coded together in network byte 1193 order in two consecutive octets. Note also that Sub-Option Data may 1194 be up to 1023 bytes in length. This allows ample space for encoding 1195 large objects (e.g., ascii character strings, security codes, etc.), 1196 while a single OMNI option is limited to 2048 bytes the same as for 1197 any IPv6 ND option. If the Sub-Options to be coded would cause the 1198 OMNI option to exceed 2048 bytes, any remaining Sub-Options are 1199 encoded in additional OMNI options in the consecutive order of 1200 intended processing. Implementations must therefore be mindful of 1201 size limitations, and must refrain from sending IPv6 ND messages 1202 larger than the OMNI interface MTU. 1204 During processing, unrecognized Sub-Options are ignored and the next 1205 Sub-Option processed until the end of the OMNI option is reached. 1207 The following Sub-Option types and formats are defined in this 1208 document: 1210 10.1.1. Pad1 1212 0 1213 0 1 2 3 4 5 6 7 1214 +-+-+-+-+-+-+-+-+ 1215 | Sub-Type=0|x|x| 1216 +-+-+-+-+-+-+-+-+ 1218 Figure 6: Pad1 1220 o Sub-Type is set to 0. If multiple instances appear in the same 1221 OMNI option all are processed. 1223 o Sub-Type is followed by two 'x' bits, set randomly on transmission 1224 and ignored on receipt. Pad1 therefore consists of a whole single 1225 octet with the most significant 6 bits set to 0, and with no Sub- 1226 Length or Sub-Option Data fields following. 1228 10.1.2. PadN 1230 0 1 2 1231 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 1232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1233 | Sub-Type=1| Sub-length=N | N padding octets ... 1234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1236 Figure 7: PadN 1238 o Sub-Type is set to 1. If multiple instances appear in the same 1239 OMNI option all are processed. 1241 o Sub-Length is set to N (from 0 to 1023 being the number of padding 1242 octets that follow. 1244 o Sub-Option Data consists of N zero-valued octets. 1246 10.1.3. Interface Attributes 1248 The Interface Attributes sub-option provides L2 forwarding 1249 information for the multilink conceptual sending algorithm discussed 1250 in Section 12. The L2 information is used for selecting among 1251 potentially multiple candidate underlying interfaces that can be used 1252 to forward packets to the neighbor based on factors such as DSCP 1253 preferences and link quality. Interface Attributes further include 1254 link-layer address information to be used for either OAL 1255 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1256 can be avoided). The Interface Attributes format and contents are 1257 given in Figure 8 below: 1259 0 1 2 3 1260 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1262 | Sub-Type=2| Sub-length=N | ifIndex | ifType | 1263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1264 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1266 | LHS (bits 8 - 31) | ~ 1267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1268 ~ ~ 1269 ~ Link Layer Address (L2ADDR) ~ 1270 ~ ~ 1271 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1272 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1274 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1276 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1279 Figure 8: Interface Attributes 1281 o Sub-Type is set to 2. If multiple instances with different 1282 ifIndex values appear in the same OMNI option all are processed; 1283 if multiple instances with the same ifIndex value appear, the 1284 first is processed and all others are ignored. 1286 o Sub-Length is set to N (from 4 to 1023) that encodes the number of 1287 Sub-Option Data octets that follow. 1289 o Sub-Option Data contains an "Interface Attribute" option encoded 1290 as follows (note that the first four octets must be present): 1292 * ifIndex is set to an 8-bit integer value corresponding to a 1293 specific underlying interface the same as specified above for 1294 the OMNI option header S/T-ifIndex. An OMNI option may include 1295 multiple Interface Attributes Sub-Options, with each distinct 1296 ifIndex value pertaining to a different underlying interface. 1297 The OMNI option will often include an Interface Attributes Sub- 1298 Option with the same ifIndex value that appears in the S/ 1299 T-ifIndex. In that case, the actual encapsulation address of 1300 the received IPv6 ND message should be compared with the L2ADDR 1301 encoded in the Sub-Option (see below); if the addresses are 1302 different (or, if L2ADDR is absent) the presence of a NAT is 1303 assumed. 1305 * ifType is set to an 8-bit integer value corresponding to the 1306 underlying interface identified by ifIndex. The value 1307 represents an OMNI interface-specific 8-bit mapping for the 1308 actual IANA ifType value registered in the 'IANAifType-MIB' 1309 registry [http://www.iana.org]. 1311 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1312 for the network service provider associated with this ifIndex. 1314 * Link encodes a 4-bit link metric. The value '0' means the link 1315 is DOWN, and the remaining values mean the link is UP with 1316 metric ranging from '1' ("lowest") to '15' ("highest"). 1318 * R is reserved for future use. 1320 * API - a 3-bit "Address/Preferences/Indexed" code that 1321 determines the contents of the remainder of the sub-option as 1322 follows: 1324 + When the most significant bit (i.e., "Address") is set to 1, 1325 the SRT, FMT, LHS and L2ADDR fields are included immediately 1326 following the API code; else, they are omitted. 1328 + When the next most significant bit (i.e., "Preferences") is 1329 set to 1, a preferences block is included next; else, it is 1330 omitted. (Note that if "Address" is set the preferences 1331 block immediately follows L2ADDR; else, it immediately 1332 follows the API code.) 1334 + When a preferences block is present and the least 1335 significant bit (i.e., "Indexed") is set to 0, the block is 1336 encoded in "Simplex" form as shown in Figure 8; else it is 1337 encoded in "Indexed" form as discussed below. 1339 * When API indicates that an "Address" is included, the following 1340 fields appear in consecutive order (else, they are omitted): 1342 + SRT - a 5-bit Segment Routing Topology prefix length value 1343 that (when added to 96) determines the prefix length to 1344 apply to the ULA formed from concatenating [ULA*]::/96 with 1345 the 32 bit LHS MSID value that follows. For example, the 1346 value 16 corresponds to the prefix length 112. 1348 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1349 the included Link Layer Address as follows: 1351 - When the most significant bit (i.e., "Framework") is set 1352 to 0, L2ADDR is the INET encapsulation address of a 1353 Proxy/Server; otherwise, it is the address for the 1354 Source/Target itself 1356 - When the next most significant bit (i.e., "Mode") is set 1357 to 0, the Source/Target L2ADDR is on the open INET; 1358 otherwise, it is (likely) located behind one or more 1359 NATs. 1361 - When the least significant bit (i.e., "Type") is set to 1362 0, L2ADDR includes a UDP Port Number followed by an IPv4 1363 address; else, a UDP Port Number followed by an IPv6 1364 address. 1366 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1367 path to the target. When SRT and LHS are both set to 0, the 1368 LHS is considered unspecified in this IPv6 ND message. When 1369 SRT is set to 0 and LHS is non-zero, the prefix length is 1370 set to 128. SRT and LHS together provide guidance to the 1371 OMNI interface forwarding algorithm. Specifically, if SRT/ 1372 LHS is located in the local OMNI link segment then the OMNI 1373 interface can encapsulate according to FMT/L2ADDR (following 1374 any necessary NAT traversal messaging); else, it must 1375 forward according to the OMNI link spanning tree. See 1376 [I-D.templin-intarea-6706bis] for further discussion. 1378 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1379 and identifies the link-layer address (i.e., the 1380 encapsulation address) of the source/target. The UDP Port 1381 Number appears in the first two octets and the IP address 1382 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1383 The Port Number and IP address are recorded in ones- 1384 compliment "obfuscated" form per [RFC4380]. The OMNI 1385 interface forwarding algorithm uses FMT/L2ADDR to determine 1386 the encapsulation address for forwarding when SRT/LHS is 1387 located in the local OMNI link segment. Note that if the 1388 target is behind a NAT, L2ADDR will contain the mapped INET 1389 address stored in the NAT; otherwise, L2ADDR will contain 1390 the native INET information of the target itself. 1392 * When API indicates that "Preferences" are included, a 1393 preferences block appears as the remainder of the Sub-Option as 1394 a series of Bitmaps and P[*] values. In "Simplex" form, the 1395 index for each singleton Bitmap octet is inferred from its 1396 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1397 In "Indexed" form, each Bitmap is preceded by an Index octet 1398 that encodes a value "i" = (0 - 255) as the index for its 1399 companion Bitmap as follows: 1401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1402 | Index=i | Bitmap(i) |P[*] values ... 1403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1405 Figure 9 1407 * The preferences consist of a first (simplex/indexed) Bitmap 1408 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1409 2-bit P[*] values, followed by a second Bitmap (i), followed by 1410 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1411 the bits of each Bitmap(i) that are set to '1'' indicate the 1412 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1413 that follow; if any Bitmap(i) bits are '0', then the 1414 corresponding P[*] block is instead omitted. For example, if 1415 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1416 followed by the block with P[04]-P[07], etc., and ending with 1417 the block with P[28]-P[31] are included (as shown in Figure 8). 1418 The next Bitmap(i) is then consulted with its bits indicating 1419 which P[*] blocks follow, etc. out to the end of the Sub- 1420 Option. 1422 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1423 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1424 preference for underlying interface selection purposes. Not 1425 all P[*] values need to be included in the OMNI option of each 1426 IPv6 ND message received. Any P[*] values represented in an 1427 earlier OMNI option but omitted in the current OMNI option 1428 remain unchanged. Any P[*] values not yet represented in any 1429 OMNI option default to "medium". 1431 * The first 16 P[*] blocks correspond to the 64 Differentiated 1432 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1433 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1434 traffic classifier values P[64], P[65], P[66], etc. See 1435 Appendix A for further discussion and examples. 1437 10.1.4. Traffic Selector 1439 0 1 2 3 1440 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1441 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1442 | Sub-Type=3| Sub-length=N | ifIndex | ~ 1443 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1444 ~ ~ 1445 ~ RFC 6088 Format Traffic Selector ~ 1446 ~ ~ 1447 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1449 Figure 10: Traffic Selector 1451 o Sub-Type is set to 3. If multiple instances appear in the same 1452 OMNI option all are processed, i.e., even if the same ifIndex 1453 value appears multiple times. 1455 o Sub-Length is set to N (the number of Sub-Option Data octets that 1456 follow). 1458 o Sub-Option Data contains a 1-octet ifIndex encoded exactly as 1459 specified in Section 10.1.3, followed by an N-1 octet traffic 1460 selector formatted per [RFC6088] beginning with the "TS Format" 1461 field. The largest traffic selector for a given ifIndex is 1462 therefore 1022 octets. 1464 10.1.5. MS-Register 1466 0 1 2 3 1467 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1468 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1469 | Sub-Type=4| Sub-length=4n | MSID[1] (bits 0 - 15) | 1470 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1471 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1472 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1473 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1474 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1475 ... ... ... ... ... ... 1476 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1477 | MSID [n] (bits 16 - 32) | 1478 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1480 Figure 11: MS-Register Sub-option 1482 o Sub-Type is set to 4. If multiple instances appear in the same 1483 OMNI option all are processed. Only the first MAX_MSID values 1484 processed (whether in a single instance or multiple) are retained 1485 and all other MSIDs are ignored. 1487 o Sub-Length is set to 4n. 1489 o A list of n 4-octet MSIDs is included in the following 4n octets. 1490 The Anycast MSID value '0' in an RS message MS-Register sub-option 1491 requests the recipient to return the MSID of a nearby MSE in a 1492 corresponding RA response. 1494 10.1.6. MS-Release 1496 0 1 2 3 1497 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1499 | Sub-Type=5| Sub-length=4n | MSID[1] (bits 0 - 15) | 1500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1501 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1503 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1505 ... ... ... ... ... ... 1506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1507 | MSID [n] (bits 16 - 32) | 1508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1510 Figure 12: MS-Release Sub-option 1512 o Sub-Type is set to 5. If multiple instances appear in the same 1513 IPv6 OMNI option all are processed. Only the first MAX_MSID 1514 values processed (whether in a single instance or multiple) are 1515 retained and all other MSIDs are ignored. 1517 o Sub-Length is set to 4n. 1519 o A list of n 4 octet MSIDs is included in the following 4n octets. 1520 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1521 i.e., only non-zero values are processed. 1523 10.1.7. Network Access Identifier (NAI) 1525 0 1 2 3 1526 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1527 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1528 | Sub-Type=6| Sub-length=N |Network Access Identifier (NAI) 1529 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1531 Figure 13: Network Access Identifier (NAI) Sub-option 1533 o Sub-Type is set to 6. If multiple instances appear in the same 1534 OMNI option the first is processed and all others are ignored. 1536 o Sub-Length is set to N (i.e., the length of the encoded Network 1537 Access Identifier (NAI)). 1539 o An NAI up to 1023 octets in length is coded per [RFC7542]. 1541 10.1.8. Geo Coordinates 1543 0 1 2 3 1544 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1545 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1546 | Sub-Type=7| Sub-length=N | Geo Coordinates 1547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1549 Figure 14: Geo Coordinates Sub-option 1551 o Sub-Type is set to 7. If multiple instances appear in the same 1552 OMNI option the first is processed and all others are ignored. 1554 o Sub-Length is set to N (i.e., the length of the encoded Geo 1555 Coordinates). 1557 o A set of Geo Coordinates up to 1023 octets in length (format TBD). 1558 Includes Latitude/Longitude at a minimum; may also include 1559 additional attributes such as altitude, heading, speed, etc.). 1561 10.1.9. DHCP Unique Identifier (DUID) 1563 0 1 2 3 1564 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1566 | Sub-Type=8| Sub-length=N | DUID-Type | 1567 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1568 . . 1569 . type-specific DUID body (variable length) . 1570 . . 1571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1573 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1575 o Sub-Type is set to 8. If multiple instances appear in the same 1576 OMNI option the first is processed and all others are ignored. 1578 o Sub-Length is set to N (i.e., the length of the option beginning 1579 with the DUID-Type and continuing to the end of the type-specific 1580 body). 1582 o DUID-Type is a two-octet field coded in network byte order that 1583 determines the format and contents of the type-specific body 1584 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1585 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1586 which will occur in common operational practice. 1588 o A type-specific DUID body up to 1021 octets in length follows, 1589 formatted according to DUID-type. For example, for type 4 the 1590 body consists of a 128-bit UUID selected according to [RFC6355]. 1592 10.1.10. DHCPv6 Message 1594 0 1 2 3 1595 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1597 | Sub-Type=9| Sub-length=N | msg-type | id (octet 0) | 1598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1599 | transaction-id (octets 1-2) | | 1600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1601 | | 1602 . DHCPv6 options . 1603 . (variable number and length) . 1604 | | 1605 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1607 Figure 16: DHCPv6 Message Sub-option 1609 o Sub-Type is set to 9. If multiple instances appear in the same 1610 OMNI option the first is processed and all others are ignored. 1612 o Sub-Length is set to N (i.e., the length of the DHCPv6 message 1613 beginning with 'msg-type' and continuing to the end of the DHCPv6 1614 options). The length of the entire DHCPv6 message is therefore 1615 restricted to 1023 octets. 1617 o 'msg-type' and 'transaction-id' are coded according to Section 8 1618 of [RFC8415]. 1620 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1621 follows. 1623 11. Address Mapping - Multicast 1625 The multicast address mapping of the native underlying interface 1626 applies. The mobile router on board the MN also serves as an IGMP/ 1627 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1628 using the L2 address of the AR as the L2 address for all multicast 1629 packets. 1631 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1632 coordinate with the AR, and *NET L2 elements use MLD snooping 1633 [RFC4541]. 1635 12. Multilink Conceptual Sending Algorithm 1637 The MN's IPv6 layer selects the outbound OMNI interface according to 1638 SBM considerations when forwarding data packets from local or EUN 1639 applications to external correspondents. Each OMNI interface 1640 maintains a neighbor cache the same as for any IPv6 interface, but 1641 with additional state for multilink coordination. Each OMNI 1642 interface maintains default routes via ARs discovered as discussed in 1643 Section 13, and may configure more-specific routes discovered through 1644 means outside the scope of this specification. 1646 After a packet enters the OMNI interface, one or more outbound 1647 underlying interfaces are selected based on PBM traffic attributes, 1648 and one or more neighbor underlying interfaces are selected based on 1649 the receipt of Interface Attributes sub-options in IPv6 ND messages 1650 (see: Figure 8). Underlying interface selection for the nodes own 1651 local interfaces are based on attributes such as DSCP, application 1652 port number, cost, performance, message size, etc. OMNI interface 1653 multilink selections could also be configured to perform replication 1654 across multiple underlying interfaces for increased reliability at 1655 the expense of packet duplication. The set of all Interface 1656 Attributes received in IPv6 ND messages determine the multilink 1657 forwarding profile for selecting the neighbor's underlying 1658 interfaces. 1660 When the OMNI interface sends a packet over a selected outbound 1661 underlying interface, the OAL includes or omits a mid-layer 1662 encapsulation header as necessary as discussed in Section 5 and as 1663 determined by the L2 address information received in Interface 1664 Attributes. The OAL also performs encapsulation when the nearest AR 1665 is located multiple hops away as discussed in Section 13.1. 1667 OMNI interface multilink service designers MUST observe the BCP 1668 guidance in Section 15 [RFC3819] in terms of implications for 1669 reordering when packets from the same flow may be spread across 1670 multiple underlying interfaces having diverse properties. 1672 12.1. Multiple OMNI Interfaces 1674 MNs may connect to multiple independent OMNI links concurrently in 1675 support of SBM. Each OMNI interface is distinguished by its Anycast 1676 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 1677 configures a separate OMNI interface for each link so that multiple 1678 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 1679 layer. A different Anycast ULA is assigned to each interface, and 1680 the MN injects the service prefixes for the OMNI link instances into 1681 the EUN routing system. 1683 Applications in EUNs can use Segment Routing to select the desired 1684 OMNI interface based on SBM considerations. The Anycast ULA is 1685 written into the IPv6 destination address, and the actual destination 1686 (along with any additional intermediate hops) is written into the 1687 Segment Routing Header. Standard IP routing directs the packets to 1688 the MN's mobile router entity, and the Anycast ULA identifies the 1689 OMNI interface to be used for transmission to the next hop. When the 1690 MN receives the message, it replaces the IPv6 destination address 1691 with the next hop found in the routing header and transmits the 1692 message over the OMNI interface identified by the Anycast ULA. 1694 Multiple distinct OMNI links can therefore be used to support fault 1695 tolerance, load balancing, reliability, etc. The architectural model 1696 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1698 12.2. MN<->AR Traffic Loop Prevention 1700 After an AR has registered an MNP for a MN (see: Section 13), the AR 1701 will forward packets destined to an address within the MNP to the MN. 1702 The MN will under normal circumstances then forward the packet to the 1703 correct destination within its internal networks. 1705 If at some later time the MN loses state (e.g., after a reboot), it 1706 may begin returning packets destined to an MNP address to the AR as 1707 its default router. The AR therefore must drop any packets 1708 originating from the MN and destined to an address within the MN's 1709 registered MNP. To do so, the AR institutes the following check: 1711 o if the IP destination address belongs to a neighbor on the same 1712 OMNI interface, and if the link-layer source address is the same 1713 as one of the neighbor's link-layer addresses, drop the packet. 1715 13. Router Discovery and Prefix Registration 1717 MNs interface with the MS by sending RS messages with OMNI options 1718 under the assumption that one or more AR on the *NET will process the 1719 message and respond. The MN then configures default routes for the 1720 OMNI interface via the discovered ARs as the next hop. The manner in 1721 which the *NET ensures AR coordination is link-specific and outside 1722 the scope of this document (however, considerations for *NETs that do 1723 not provide ARs that recognize the OMNI option are discussed in 1724 Section 18). 1726 For each underlying interface, the MN sends an RS message with an 1727 OMNI option to coordinate with MSEs identified by MSID values. 1728 Example MSID discovery methods are given in [RFC5214] and include 1729 data link login parameters, name service lookups, static 1730 configuration, a static "hosts" file, etc. The MN can also send an 1731 RS with an MS-Register sub-option that includes the Anycast MSID 1732 value '0', i.e., instead of or in addition to any non-zero MSIDs. 1733 When the AR receives an RS with a MSID '0', it selects a nearby MSE 1734 (which may be itself) and returns an RA with the selected MSID in an 1735 MS-Register sub-option. The AR selects only a single wildcard MSE 1736 (i.e., even if the RS MS-Register sub-option included multiple '0' 1737 MSIDs) while also soliciting the MSEs corresponding to any non-zero 1738 MSIDs. 1740 MNs configure OMNI interfaces that observe the properties discussed 1741 in the previous section. The OMNI interface and its underlying 1742 interfaces are said to be in either the "UP" or "DOWN" state 1743 according to administrative actions in conjunction with the interface 1744 connectivity status. An OMNI interface transitions to UP or DOWN 1745 through administrative action and/or through state transitions of the 1746 underlying interfaces. When a first underlying interface transitions 1747 to UP, the OMNI interface also transitions to UP. When all 1748 underlying interfaces transition to DOWN, the OMNI interface also 1749 transitions to DOWN. 1751 When an OMNI interface transitions to UP, the MN sends RS messages to 1752 register its MNP and an initial set of underlying interfaces that are 1753 also UP. The MN sends additional RS messages to refresh lifetimes 1754 and to register/deregister underlying interfaces as they transition 1755 to UP or DOWN. The MN sends initial RS messages over an UP 1756 underlying interface with its MNP-LLA as the source and with 1757 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1758 messages include an OMNI option per Section 10 with a Preflen 1759 assertion, Interface Attributes appropriate for underlying 1760 interfaces, MS-Register/Release sub-options containing MSID values, 1761 and with any other necessary OMNI sub-options (e.g., a DUID sub- 1762 option as an identity for the MN). The S/T-ifIndex field is set to 1763 the index of the underlying interface over which the RS message is 1764 sent. 1766 ARs process IPv6 ND messages with OMNI options and act as an MSE 1767 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1768 and create a neighbor cache entry for the MN, then coordinate with 1769 any MSEs named in the Register/Release lists in a manner outside the 1770 scope of this document. When an MSE processes the OMNI information, 1771 it first validates the prefix registration information then injects/ 1772 withdraws the MNP in the routing/mapping system and caches/discards 1773 the new Preflen, MNP and Interface Attributes. The MSE then informs 1774 the AR of registration success/failure, and the AR returns an RA 1775 message to the MN with an OMNI option per Section 10. 1777 The AR returns the RA message via the same underlying interface of 1778 the MN over which the RS was received, and with destination address 1779 set to the MNP-LLA (i.e., unicast), with source address set to its 1780 own LLA, and with an OMNI option with S/T-ifIndex set to the value 1781 included in the RS. The OMNI option also includes a Preflen 1782 confirmation, Interface Attributes, MS-Register/Release and any other 1783 necessary OMNI sub-options (e.g., a DUID sub-option as an identity 1784 for the AR). The RA also includes any information for the link, 1785 including RA Cur Hop Limit, M and O flags, Router Lifetime, Reachable 1786 Time and Retrans Timer values, and includes any necessary options 1787 such as: 1789 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1791 o RIOs [RFC4191] with more-specific routes. 1793 o an MTU option that specifies the maximum acceptable packet size 1794 for this underlying interface. 1796 The AR MAY also send periodic and/or event-driven unsolicited RA 1797 messages per [RFC4861]. In that case, the S/T-ifIndex field in the 1798 OMNI header of the unsolicited RA message identifies the target 1799 underlying interface of the destination MN. 1801 The AR can combine the information from multiple MSEs into one or 1802 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 1803 Each aggregate RA includes an OMNI option with MS-Register/Release 1804 sub-options with the MSEs represented by the aggregate. If an 1805 aggregate is sent, the RA message contents must consistently 1806 represent the combined information advertised by all represented 1807 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 1808 address, the MN determines the addresses of the represented MSEs by 1809 examining the MS-Register/Release OMNI sub-options. 1811 When the MN receives the RA message, it creates an OMNI interface 1812 neighbor cache entry for each MSID that has confirmed MNP 1813 registration via the L2 address of this AR. If the MN connects to 1814 multiple *NETs, it records the additional L2 AR addresses in each 1815 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1816 then configures a default route via the MSE that returned the RA 1817 message, and assigns the Subnet Router Anycast address corresponding 1818 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 1819 manages its underlying interfaces according to their states as 1820 follows: 1822 o When an underlying interface transitions to UP, the MN sends an RS 1823 over the underlying interface with an OMNI option. The OMNI 1824 option contains at least one Interface Attribute sub-option with 1825 values specific to this underlying interface, and may contain 1826 additional Interface Attributes specific to other underlying 1827 interfaces. The option also includes any MS-Register/Release sub- 1828 options. 1830 o When an underlying interface transitions to DOWN, the MN sends an 1831 RS or unsolicited NA message over any UP underlying interface with 1832 an OMNI option containing an Interface Attribute sub-option for 1833 the DOWN underlying interface with Link set to '0'. The MN sends 1834 an RS when an acknowledgement is required, or an unsolicited NA 1835 when reliability is not thought to be a concern (e.g., if 1836 redundant transmissions are sent on multiple underlying 1837 interfaces). 1839 o When the Router Lifetime for a specific AR nears expiration, the 1840 MN sends an RS over the underlying interface to receive a fresh 1841 RA. If no RA is received, the MN can send RS messages to an 1842 alternate MSID in case the current MSID has failed. If no RS 1843 messages are received even after trying to contact alternate 1844 MSIDs, the MN marks the underlying interface as DOWN. 1846 o When a MN wishes to release from one or more current MSIDs, it 1847 sends an RS or unsolicited NA message over any UP underlying 1848 interfaces with an OMNI option with a Release MSID. Each MSID 1849 then withdraws the MNP from the routing/mapping system and informs 1850 the AR that the release was successful. 1852 o When all of a MNs underlying interfaces have transitioned to DOWN 1853 (or if the prefix registration lifetime expires), any associated 1854 MSEs withdraw the MNP the same as if they had received a message 1855 with a release indication. 1857 The MN is responsible for retrying each RS exchange up to 1858 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1859 seconds until an RA is received. If no RA is received over an UP 1860 underlying interface (i.e., even after attempting to contact 1861 alternate MSEs), the MN declares this underlying interface as DOWN. 1863 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1864 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1865 returns an internally-generated RA message as though the message 1866 originated from an IPv6 router. The internally-generated RA message 1867 contains configuration information that is consistent with the 1868 information received from the RAs generated by the MS. Whether the 1869 OMNI interface IPv6 ND messaging process is initiated from the 1870 receipt of an RS message from the IPv6 layer is an implementation 1871 matter. Some implementations may elect to defer the IPv6 ND 1872 messaging process until an RS is received from the IPv6 layer, while 1873 others may elect to initiate the process proactively. Still other 1874 deployments may elect to administratively disable the ordinary RS/RA 1875 messaging used by the IPv6 layer over the OMNI interface, since they 1876 are not required to drive the internal RS/RA processing. (Note that 1877 this same logic applies to IPv4 implementations that employ ICMP- 1878 based Router Discovery per [RFC1256].) 1880 Note: The Router Lifetime value in RA messages indicates the time 1881 before which the MN must send another RS message over this underlying 1882 interface (e.g., 600 seconds), however that timescale may be 1883 significantly longer than the lifetime the MS has committed to retain 1884 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1885 therefore responsible for keeping MS state alive on a shorter 1886 timescale than the MN is required to do on its own behalf. 1888 Note: On multicast-capable underlying interfaces, MNs should send 1889 periodic unsolicited multicast NA messages and ARs should send 1890 periodic unsolicited multicast RA messages as "beacons" that can be 1891 heard by other nodes on the link. If a node fails to receive a 1892 beacon after a timeout value specific to the link, it can initiate a 1893 unicast exchange to test reachability. 1895 Note: if an AR acting as a proxy forwards a MN's RS message to 1896 another node acting as an MSE using UDP/IP encapsulation, it must use 1897 a distinct UDP source port number for each MN. This allows the MSE 1898 to distinguish different MNs behind the same AR at the link-layer, 1899 whereas the link-layer addresses would otherwise be 1900 indistinguishable. 1902 Note: when an AR acting as an MSE returns an RA to an INET Client, it 1903 includes an OMNI option with an Interface Attributes sub-option with 1904 ifIndex set to 0 and with SRT, FMT, LHS and L2ADDR information for 1905 its INET interface. This provides the Client with partition prefix 1906 context regarding the local OMNI link segment. 1908 13.1. Router Discovery in IP Multihop and IPv4-Only Networks 1910 On some *NETs, a MN may be located multiple IP hops away from the 1911 nearest AR. Forwarding through IP multihop *NETs is conducted 1912 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1913 Network (MANET) routing protocol over omni-directional wireless 1914 interfaces, an inter-domain routing protocol in an enterprise 1915 network, etc.). These *NETs could be either IPv6-enabled or 1916 IPv4-only, while IPv4-only *NETs could be either multicast-capable or 1917 unicast-only (note that for IPv4-only *NETs the following procedures 1918 apply for both single-hop and multihop cases). 1920 A MN located potentially multiple *NET hops away from the nearest AR 1921 prepares an RS message with source address set to either its MNP-LLA 1922 or a Temporary LLA, and with destination set to link-scoped All- 1923 Routers multicast the same as discussed above. For IPv6-enabled 1924 *NETs, the MN then encapsulates the message in an IPv6 header with 1925 source address set to the ULA corresponding to the LLA source address 1926 and with destination set to either a unicast or anycast ADM-ULA. For 1927 IPv4-only *NETs, the MN instead encapsulates the RS message in an 1928 IPv4 header with source address set to the node's own IPv4 address 1929 and with destination address set to either the unicast IPv4 address 1930 of an AR [RFC5214] or an IPv4 anycast address reserved for OMNI. The 1931 MN then sends the encapsulated RS message via the *NET interface, 1932 where it will be forwarded by zero or more intermediate *NET hops. 1934 When an intermediate *NET hop that participates in the routing 1935 protocol receives the encapsulated RS, it forwards the message 1936 according to its routing tables (note that an intermediate node could 1937 be a fixed infrastructure element or another MN). This process 1938 repeats iteratively until the RS message is received by a penultimate 1939 *NET hop within single-hop communications range of an AR, which 1940 forwards the message to the AR. 1942 When the AR receives the message, it decapsulates the RS and 1943 coordinates with the MS the same as for an ordinary link-local RS, 1944 since the inner Hop Limit will not have been decremented by the 1945 multihop forwarding process. The AR then prepares an RA message with 1946 source address set to its own ADM-LLA and destination address set to 1947 the LLA of the original MN, then encapsulates the message in an IPv4/ 1948 IPv6 header with source address set to its own IPv4/ULA address and 1949 with destination set to the encapsulation source of the RS. 1951 The AR then forwards the message to an *NET node within 1952 communications range, which forwards the message according to its 1953 routing tables to an intermediate node. The multihop forwarding 1954 process within the *NET continues repetitively until the message is 1955 delivered to the original MN, which decapsulates the message and 1956 performs autoconfiguration the same as if it had received the RA 1957 directly from the AR as an on-link neighbor. 1959 Note: An alternate approach to multihop forwarding via IPv6 1960 encapsulation would be to statelessly translate the IPv6 LLAs into 1961 ULAs and forward the messages without encapsulation. This would 1962 violate the [RFC4861] requirement that certain IPv6 ND messages must 1963 use link-local addresses and must not be accepted if received with 1964 Hop Limit less than 255. This document therefore advocates 1965 encapsulation since the overhead is nominal considering the 1966 infrequent nature and small size of IPv6 ND messages. Future 1967 documents may consider encapsulation avoidance through translation 1968 while updating [RFC4861]. 1970 Note: An alternate approach to multihop forwarding via IPv4 1971 encapsulation would be to employ IPv6/IPv4 protocol translation. 1972 However, for IPv6 ND messages the LLAs would be truncated due to 1973 translation and the OMNI Router and Prefix Discovery services would 1974 not be able to function. The use of IPv4 encapsulation is therefore 1975 indicated. 1977 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 1978 of a new IPv4 /24 prefix allocation, but this may be difficult to 1979 obtain given IPv4 address exhaustion. An alternative would be to re- 1980 purpose the prefix 192.88.99.0 which has been set aside from its 1981 former use by [RFC7526]. 1983 13.2. MS-Register and MS-Release List Processing 1985 When a MN sends an RS message with an OMNI option via an underlying 1986 interface to an AR, the MN must convey its knowledge of its 1987 currently-associated MSEs. Initially, the MN will have no associated 1988 MSEs and should therefore include an MS-Register sub-option with the 1989 single MSID value 0 which requests the AR to select and assign an 1990 MSE. The AR will then return an RA message with source address set 1991 to the ADM-LLA of the selected MSE. 1993 As the MN activates additional underlying interfaces, it can 1994 optionally include an MS-Register sub-option with MSID value 0, or 1995 with non-zero MSIDs for MSEs discovered from previous RS/RA 1996 exchanges. The MN will thus eventually begin to learn and manage its 1997 currently active set of MSEs, and can register with new MSEs or 1998 release from former MSEs with each successive RS/RA exchange. As the 1999 MN's MSE constituency grows, it alone is responsible for including or 2000 omitting MSIDs in the MS-Register/Release lists it sends in RS 2001 messages. The inclusion or omission of MSIDs determines the MN's 2002 interface to the MS and defines the manner in which MSEs will 2003 respond. The only limiting factor is that the MN should include no 2004 more than MAX_MSID values in each list per each IPv6 ND message, and 2005 should avoid duplication of entries in each list unless it wants to 2006 increase likelihood of control message delivery. 2008 When an AR receives an RS message sent by a MN with an OMNI option, 2009 the option will contain zero or more MS-Register and MS-Release sub- 2010 options containing MSIDs. After processing the OMNI option, the AR 2011 will have a list of zero or more MS-Register MSIDs and a list of zero 2012 or more of MS-Release MSIDs. The AR then processes the lists as 2013 follows: 2015 o For each list, retain the first MAX_MSID values in the list and 2016 discard any additional MSIDs (i.e., even if there are duplicates 2017 within a list). 2019 o Next, for each MSID in the MS-Register list, remove all matching 2020 MSIDs from the MS-Release list. 2022 o Next, proceed according to whether the AR's own MSID or the value 2023 0 appears in the MS-Register list as follows: 2025 * If yes, send an RA message directly back to the MN and send a 2026 proxy copy of the RS message to each additional MSID in the MS- 2027 Register list with the MS-Register/Release lists omitted. 2028 Then, send a uNA message to each MSID in the MS-Release list 2029 with the MS-Register/Release lists omitted and with an OMNI 2030 header with S/T-ifIndex set to 0. 2032 * If no, send a proxy copy of the RS message to each additional 2033 MSID in the MS-Register list with the MS-Register list omitted. 2034 For the first MSID, include the original MS-Release list; for 2035 all other MSIDs, omit the MS-Release list. 2037 Each proxy copy of the RS message will include an OMNI option and 2038 encapsulation header with the ADM-ULA of the AR as the source and the 2039 ADM-ULA of the Register MSE as the destination. When the Register 2040 MSE receives the proxy RS message, if the message includes an MS- 2041 Release list the MSE sends a uNA message to each additional MSID in 2042 the Release list. The Register MSE then sends an RA message back to 2043 the (Proxy) AR wrapped in an OMNI encapsulation header with source 2044 and destination addresses reversed, and with RA destination set to 2045 the MNP-LLA of the MN. When the AR receives this RA message, it 2046 sends a proxy copy of the RA to the MN. 2048 Each uNA message (whether send by the first-hop AR or by a Register 2049 MSE) will include an OMNI option and an encapsulation header with the 2050 ADM-ULA of the Register MSE as the source and the ADM-ULA of the 2051 Release ME as the destination. The uNA informs the Release MSE that 2052 its previous relationship with the MN has been released and that the 2053 source of the uNA message is now registered. The Release MSE must 2054 then note that the subject MN of the uNA message is now "departed", 2055 and forward any subsequent packets destined to the MN to the Register 2056 MSE. 2058 Note that it is not an error for the MS-Register/Release lists to 2059 include duplicate entries. If duplicates occur within a list, the AR 2060 will generate multiple proxy RS and/or uNA messages - one for each 2061 copy of the duplicate entries. 2063 13.3. DHCPv6-based Prefix Registration 2065 When a MN is not pre-provisioned with an MNP-LLA (or, when multiple 2066 MNPs are needed), it will require the AR to select MNPs on its behalf 2067 and set up the correct routing state within the MS. The DHCPv6 2068 service [RFC8415] supports this requirement. 2070 When an MN needs to have the AR select MNPs, it sends an RS message 2071 with a Temporary LLA as the source and with DHCPv6 Message sub-option 2072 containing a Client Identifier, one or more IA_PD options and a Rapid 2073 Commit option. The MN also sets the 'msg-type' field to "Solicit", 2074 and includes a 3-octet 'transaction-id'. 2076 When the AR receives the RS message, it extracts the DHCPv6 message 2077 from the OMNI option. The AR then acts as a "Proxy DHCPv6 Client" in 2078 a message exchange with the locally-resident DHCPv6 server, which 2079 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 2080 (If the AR wishes to defer creation of MN state until the DHCPv6 2081 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 2082 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 2083 forward/reply exchange with Relay Message and Interface ID options.) 2085 When the AR receives the DHCPv6 Reply, it adds routes to the routing 2086 system and creates MNP-LLAs based on the delegated MNPs. The AR then 2087 sends an RA back to the MN with the DHCPv6 Reply message included in 2088 an OMNI DHCPv6 message sub-option. If the RS message source address 2089 was a Temporary address, the AR includes one of the (newly-created) 2090 MNP-LLAs as the RA destination address. The MN then creates a 2091 default route, assigns Subnet Router Anycast addresses and uses the 2092 RA destination address as its primary MNP-LLA. The MN will then use 2093 this primary MNP-LLA as the source address of any IPv6 ND messages it 2094 sends as long as it retains ownership of the MNP. 2096 Note: After a MN performs a DHCPv6-based prefix registration exchange 2097 with a first AR, it would need to repeat the exchange with each 2098 additional MSE it registers with. In that case, the MN supplies the 2099 MNP delegations received from the first AR in the IA_PD fields of a 2100 DHCPv6 message when it engages the additional MSEs. 2102 14. Secure Redirection 2104 If the *NET link model is multiple access, the AR is responsible for 2105 assuring that address duplication cannot corrupt the neighbor caches 2106 of other nodes on the link. When the MN sends an RS message on a 2107 multiple access *NET link, the AR verifies that the MN is authorized 2108 to use the address and returns an RA with a non-zero Router Lifetime 2109 only if the MN is authorized. 2111 After verifying MN authorization and returning an RA, the AR MAY 2112 return IPv6 ND Redirect messages to direct MNs located on the same 2113 *NET link to exchange packets directly without transiting the AR. In 2114 that case, the MNs can exchange packets according to their unicast L2 2115 addresses discovered from the Redirect message instead of using the 2116 dogleg path through the AR. In some *NET links, however, such direct 2117 communications may be undesirable and continued use of the dogleg 2118 path through the AR may provide better performance. In that case, 2119 the AR can refrain from sending Redirects, and/or MNs can ignore 2120 them. 2122 15. AR and MSE Resilience 2124 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2125 [RFC5798] configurations so that service continuity is maintained 2126 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2127 the (redundant) ARs is currently providing service, and any service 2128 discontinuity will be limited to the failover time supported by VRRP. 2129 Widely deployed public domain implementations of VRRP are available. 2131 MSEs SHOULD use high availability clustering services so that 2132 multiple redundant systems can provide coordinated response to 2133 failures. As with VRRP, widely deployed public domain 2134 implementations of high availability clustering services are 2135 available. Note that special-purpose and expensive dedicated 2136 hardware is not necessary, and public domain implementations can be 2137 used even between lightweight virtual machines in cloud deployments. 2139 16. Detecting and Responding to MSE Failures 2141 In environments where fast recovery from MSE failure is required, ARs 2142 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2143 manner that parallels Bidirectional Forwarding Detection (BFD) 2144 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2145 react to failures so that cached information is re-established 2146 through alternate paths. Proactive NUD control messaging is carried 2147 only over well-connected ground domain networks (i.e., and not low- 2148 end *NET links such as aeronautical radios) and can therefore be 2149 tuned for rapid response. 2151 ARs perform proactive NUD for MSEs for which there are currently 2152 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2153 of the outage by sending multicast RA messages on the *NET interface. 2154 The AR sends RA messages to MNs via the *NET interface with an OMNI 2155 option with a Release ID for the failed MSE, and with destination 2156 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2158 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2159 by small delays [RFC4861]. Any MNs on the *NET interface that have 2160 been using the (now defunct) MSE will receive the RA messages and 2161 associate with a new MSE. 2163 17. Transition Considerations 2165 When a MN connects to an *NET link for the first time, it sends an RS 2166 message with an OMNI option. If the first hop AR recognizes the 2167 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2168 as the destination and with an OMNI option included. The MN then 2169 engages the AR according to the OMNI link model specified above. If 2170 the first hop AR is a legacy IPv6 router, however, it instead returns 2171 an RA message with no OMNI option and with a non-OMNI unicast source 2172 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2173 according to the legacy IPv6 link model and without the OMNI 2174 extensions specified in this document. 2176 If the *NET link model is multiple access, there must be assurance 2177 that address duplication cannot corrupt the neighbor caches of other 2178 nodes on the link. When the MN sends an RS message on a multiple 2179 access *NET link with an LLA source address and an OMNI option, ARs 2180 that recognize the option ensure that the MN is authorized to use the 2181 address and return an RA with a non-zero Router Lifetime only if the 2182 MN is authorized. ARs that do not recognize the option instead 2183 return an RA that makes no statement about the MN's authorization to 2184 use the source address. In that case, the MN should perform 2185 Duplicate Address Detection to ensure that it does not interfere with 2186 other nodes on the link. 2188 An alternative approach for multiple access *NET links to ensure 2189 isolation for MN / AR communications is through L2 address mappings 2190 as discussed in Appendix C. This arrangement imparts a (virtual) 2191 point-to-point link model over the (physical) multiple access link. 2193 18. OMNI Interfaces on the Open Internet 2195 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2196 the open Internet without an OMNI-aware first-hop AR receive RA 2197 messages that do not include an OMNI option, while OMNI interfaces 2198 configured over IPv4-only underlying interfaces do not receive any 2199 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2200 without an OMNI option configure addresses, on-link prefixes, etc. on 2201 the underlying interface that received the RA according to standard 2202 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2203 interfaces configured over IPv4-only underlying interfaces configure 2204 IPv4 address information on the underlying interfaces using 2205 mechanisms such as DHCPv4 [RFC2131]. 2207 OMNI interfaces configured over underlying interfaces that connect to 2208 the open Internet can apply security services such as VPNs to connect 2209 to an MSE, or can establish a direct link to an MSE through some 2210 other means (see Section 4). In environments where an explicit VPN 2211 or direct link may be impractical, OMNI interfaces can instead use 2212 UDP/IP encapsulation and HMAC-based message authentication per 2213 [RFC6081][RFC4380]. 2215 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2216 interfaces send control plane messages to interface with the MS, 2217 including RS/RA messages used according to Section 13 and Neighbor 2218 Solicitation (NS) and Neighbor Advertisement (NA) messages used for 2219 address resolution / route optimization (see: 2220 [I-D.templin-intarea-6706bis]). The control plane messages must be 2221 authenticated while data plane messages are delivered the same as for 2222 ordinary best-effort Internet traffic with basic source address-based 2223 data origin verification. Data plane communications via OMNI 2224 interfaces that connect over the open Internet without an explicit 2225 VPN should therefore employ transport- or higher-layer security to 2226 ensure integrity and/or confidentiality. 2228 OMNI interfaces in the open Internet are often located behind NATs. 2229 The OMNI interface accommodates NAT traversal using UDP/IP 2230 encapsulation and the mechanisms discussed in 2231 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 2233 19. Time-Varying MNPs 2235 In some use cases, it is desirable, beneficial and efficient for the 2236 MN to receive a constant MNP that travels with the MN wherever it 2237 moves. For example, this would allow air traffic controllers to 2238 easily track aircraft, etc. In other cases, however (e.g., 2239 intelligent transportation systems), the MN may be willing to 2240 sacrifice a modicum of efficiency in order to have time-varying MNPs 2241 that can be changed every so often to defeat adversarial tracking. 2243 The prefix delegation services discussed in Section 13.3 allows OMNI 2244 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2245 use a Temporary LLA as the source address of an RS message with an 2246 OMNI option with DHCPv6 Option sub-options. The MN would then be 2247 obligated to renumber its internal networks whenever its MNP (and 2248 therefore also its OMNI address) changes. This should not present a 2249 challenge for MNs with automated network renumbering services, 2250 however presents limits for the durations of ongoing sessions that 2251 would prefer to use a constant address. 2253 20. IANA Considerations 2255 The IANA is instructed to allocate an official Type number TBD from 2256 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2257 option. Implementations set Type to 253 as an interim value 2258 [RFC4727]. 2260 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2261 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2262 read as follows: 2264 Code Name Reference 2265 --- ---- --------- 2266 0 Diagnostic Packet Too Big [RFC4443] 2267 1 Advisory Packet Too Big [RFCXXXX] 2269 Figure 17: ICMPv6 Code Fields: Type 2 - Packet Too Big Values 2271 The IANA is instructed to allocate one Ethernet unicast address TBD2 2272 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 2273 Address Block - Unicast Use". 2275 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 2276 is instructed to create and maintain a new registry entitled "OMNI 2277 option Sub-Type values". Initial values for the OMNI option Sub-Type 2278 values registry are given below; future assignments are to be made 2279 through Expert Review [RFC8126]. 2281 Value Sub-Type name Reference 2282 ----- ------------- ---------- 2283 0 Pad1 [RFCXXXX] 2284 1 PadN [RFCXXXX] 2285 2 Interface Attributes [RFCXXXX] 2286 3 Traffic Selector [RFCXXXX] 2287 4 MS-Register [RFCXXXX] 2288 5 MS-Release [RFCXXXX] 2289 6 Network Access Identifier [RFCXXXX] 2290 7 Geo Coordinates [RFCXXXX] 2291 8 DHCP Unique Identifier (DUID) [RFCXXXX] 2292 9 DHCPv6 Message [RFCXXXX] 2293 10-61 Unassigned 2294 62 Experimental [RFCXXXX] 2295 63 Reserved [RFCXXXX] 2297 Figure 18: OMNI Option Sub-Type Values 2299 21. Security Considerations 2301 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 2302 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 2303 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 2304 confirmation and/or time synchronization is needed. 2306 OMNI interfaces configured over secured ANET interfaces inherit the 2307 physical and/or link-layer security properties (i.e., "protected 2308 spectrum") of the connected ANETs. OMNI interfaces configured over 2309 open INET interfaces can use symmetric securing services such as VPNs 2310 or can by some other means establish a direct link. When a VPN or 2311 direct link may be impractical, however, an asymmetric security 2312 service such as the authentication option specified in [RFC4380] or 2313 other protocol control message security mechanisms may be necessary. 2314 While the OMNI link protects control plane messaging, applications 2315 must still employ end-to-end transport- or higher-layer security 2316 services to protect the data plane. 2318 The Mobility Service MUST provide strong network layer security for 2319 control plane messages and forwarding path integrity for data plane 2320 messages. In one example, the AERO service 2321 [I-D.templin-intarea-6706bis] constructs a spanning tree between 2322 mobility service elements and secures the links in the spanning tree 2323 with network layer security mechanisms such as IPsec [RFC4301] or 2324 Wireguard. Control plane messages are then constrained to travel 2325 only over the secured spanning tree paths and are therefore protected 2326 from attack or eavesdropping. Since data plane messages can travel 2327 over route optimized paths that do not strictly follow the spanning 2328 tree, however, end-to-end transport- or higher-layer security 2329 services are still required. 2331 Security considerations for specific access network interface types 2332 are covered under the corresponding IP-over-(foo) specification 2333 (e.g., [RFC2464], [RFC2492], etc.). 2335 Security considerations for IPv6 fragmentation and reassembly are 2336 discussed in Section 5.1. 2338 22. Implementation Status 2340 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 2341 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 2342 Newer specification versions will be tagged in upcoming releases. 2343 First public release expected before the end of 2020. 2345 23. Acknowledgements 2347 The first version of this document was prepared per the consensus 2348 decision at the 7th Conference of the International Civil Aviation 2349 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2350 2019. Consensus to take the document forward to the IETF was reached 2351 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2352 Attendees and contributors included: Guray Acar, Danny Bharj, 2353 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2354 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2355 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2356 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2357 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2358 Fryderyk Wrobel and Dongsong Zeng. 2360 The following individuals are acknowledged for their useful comments: 2361 Michael Matyas, Madhu Niraula, Greg Saccone, Stephane Tamalet, Eric 2362 Vyncke. Pavel Drasil, Zdenek Jaron and Michal Skorepa are recognized 2363 for their many helpful ideas and suggestions. Madhuri Madhava 2364 Badgandi, Katherine Tran, and Vijayasarathy Rajagopalan are 2365 acknowledged for their hard work on the implementation and insights 2366 that led to improvements to the spec. 2368 Discussions on the IETF 6man and atn mailing lists during the fall of 2369 2020 suggested additional points to consider. The authors gratefully 2370 acknowledge the list members who contributed valuable insights 2371 through those discussions. Eric Vyncke and Erik Kline were the 2372 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 2373 at the time the document was developed; they are all gratefully 2374 acknowledged for their many helpful insights. 2376 This work is aligned with the NASA Safe Autonomous Systems Operation 2377 (SASO) program under NASA contract number NNA16BD84C. 2379 This work is aligned with the FAA as per the SE2025 contract number 2380 DTFAWA-15-D-00030. 2382 24. References 2384 24.1. Normative References 2386 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2387 DOI 10.17487/RFC0791, September 1981, 2388 . 2390 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2391 Requirement Levels", BCP 14, RFC 2119, 2392 DOI 10.17487/RFC2119, March 1997, 2393 . 2395 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2396 "Definition of the Differentiated Services Field (DS 2397 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2398 DOI 10.17487/RFC2474, December 1998, 2399 . 2401 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2402 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2403 DOI 10.17487/RFC3971, March 2005, 2404 . 2406 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2407 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2408 November 2005, . 2410 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2411 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2412 . 2414 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2415 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2416 2006, . 2418 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2419 Control Message Protocol (ICMPv6) for the Internet 2420 Protocol Version 6 (IPv6) Specification", STD 89, 2421 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2422 . 2424 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2425 ICMPv6, UDP, and TCP Headers", RFC 4727, 2426 DOI 10.17487/RFC4727, November 2006, 2427 . 2429 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2430 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2431 DOI 10.17487/RFC4861, September 2007, 2432 . 2434 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2435 Address Autoconfiguration", RFC 4862, 2436 DOI 10.17487/RFC4862, September 2007, 2437 . 2439 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2440 "Traffic Selectors for Flow Bindings", RFC 6088, 2441 DOI 10.17487/RFC6088, January 2011, 2442 . 2444 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2445 Hosts in a Multi-Prefix Network", RFC 8028, 2446 DOI 10.17487/RFC8028, November 2016, 2447 . 2449 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2450 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2451 May 2017, . 2453 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2454 (IPv6) Specification", STD 86, RFC 8200, 2455 DOI 10.17487/RFC8200, July 2017, 2456 . 2458 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2459 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2460 DOI 10.17487/RFC8201, July 2017, 2461 . 2463 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2464 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2465 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2466 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2467 . 2469 24.2. Informative References 2471 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 2472 Interface for Civil Aviation, IETF Liaison Statement 2473 #1676, https://datatracker.ietf.org/liaison/1676/", March 2474 2020. 2476 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 2477 Aeronautical Telecommunication Network (ATN) using 2478 Internet Protocol Suite (IPS) Standards and Protocol), 2479 Draft Edition 3 (work-in-progress)", December 2020. 2481 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 2482 Interface (FDDI), IEEE Transactions on Communications", 2483 August 1990. 2485 [I-D.ietf-6man-rfc4941bis] 2486 Gont, F., Krishnan, S., Narten, T., and R. Draves, 2487 "Temporary Address Extensions for Stateless Address 2488 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 2489 (work in progress), November 2020. 2491 [I-D.ietf-intarea-tunnels] 2492 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2493 Architecture", draft-ietf-intarea-tunnels-10 (work in 2494 progress), September 2019. 2496 [I-D.ietf-ipwave-vehicular-networking] 2497 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 2498 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 2499 ipwave-vehicular-networking-19 (work in progress), July 2500 2020. 2502 [I-D.templin-6man-dhcpv6-ndopt] 2503 Templin, F., "A Unified Stateful/Stateless Configuration 2504 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-11 2505 (work in progress), January 2021. 2507 [I-D.templin-6man-lla-type] 2508 Templin, F., "The IPv6 Link-Local Address Type Field", 2509 draft-templin-6man-lla-type-02 (work in progress), 2510 November 2020. 2512 [I-D.templin-intarea-6706bis] 2513 Templin, F., "Asymmetric Extended Route Optimization 2514 (AERO)", draft-templin-intarea-6706bis-87 (work in 2515 progress), January 2021. 2517 [IPV4-GUA] 2518 Postel, J., "IPv4 Address Space Registry, 2519 https://www.iana.org/assignments/ipv4-address-space/ipv4- 2520 address-space.xhtml", December 2020. 2522 [IPV6-GUA] 2523 Postel, J., "IPv6 Global Unicast Address Assignments, 2524 https://www.iana.org/assignments/ipv6-unicast-address- 2525 assignments/ipv6-unicast-address-assignments.xhtml", 2526 December 2020. 2528 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2529 Communication Layers", STD 3, RFC 1122, 2530 DOI 10.17487/RFC1122, October 1989, 2531 . 2533 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2534 DOI 10.17487/RFC1191, November 1990, 2535 . 2537 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2538 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2539 . 2541 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2542 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2543 . 2545 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2546 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2547 . 2549 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2550 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2551 . 2553 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2554 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2555 December 1998, . 2557 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2558 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2559 . 2561 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2562 Domains without Explicit Tunnels", RFC 2529, 2563 DOI 10.17487/RFC2529, March 1999, 2564 . 2566 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2567 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2568 . 2570 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 2571 DOI 10.17487/RFC3330, September 2002, 2572 . 2574 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2575 Considered Useful", BCP 82, RFC 3692, 2576 DOI 10.17487/RFC3692, January 2004, 2577 . 2579 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2580 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2581 DOI 10.17487/RFC3810, June 2004, 2582 . 2584 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2585 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2586 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2587 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2588 . 2590 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2591 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2592 2004, . 2594 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 2595 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 2596 DOI 10.17487/RFC4271, January 2006, 2597 . 2599 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2600 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2601 December 2005, . 2603 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2604 Network Address Translations (NATs)", RFC 4380, 2605 DOI 10.17487/RFC4380, February 2006, 2606 . 2608 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2609 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2610 2006, . 2612 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 2613 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 2614 . 2616 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2617 "Considerations for Internet Group Management Protocol 2618 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2619 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2620 . 2622 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2623 "Internet Group Management Protocol (IGMP) / Multicast 2624 Listener Discovery (MLD)-Based Multicast Forwarding 2625 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2626 August 2006, . 2628 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 2629 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 2630 . 2632 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2633 Errors at High Data Rates", RFC 4963, 2634 DOI 10.17487/RFC4963, July 2007, 2635 . 2637 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2638 Advertisement Flags Option", RFC 5175, 2639 DOI 10.17487/RFC5175, March 2008, 2640 . 2642 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2643 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2644 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2645 . 2647 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2648 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2649 DOI 10.17487/RFC5214, March 2008, 2650 . 2652 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2653 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2654 . 2656 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2657 Version 3 for IPv4 and IPv6", RFC 5798, 2658 DOI 10.17487/RFC5798, March 2010, 2659 . 2661 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2662 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2663 . 2665 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2666 DOI 10.17487/RFC6081, January 2011, 2667 . 2669 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 2670 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 2671 DOI 10.17487/RFC6221, May 2011, 2672 . 2674 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2675 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2676 DOI 10.17487/RFC6355, August 2011, 2677 . 2679 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2680 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2681 2012, . 2683 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 2684 with IPv6 Neighbor Discovery", RFC 6980, 2685 DOI 10.17487/RFC6980, August 2013, 2686 . 2688 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2689 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2690 DOI 10.17487/RFC7084, November 2013, 2691 . 2693 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2694 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2695 Boundary in IPv6 Addressing", RFC 7421, 2696 DOI 10.17487/RFC7421, January 2015, 2697 . 2699 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 2700 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 2701 DOI 10.17487/RFC7526, May 2015, 2702 . 2704 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2705 DOI 10.17487/RFC7542, May 2015, 2706 . 2708 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2709 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2710 February 2016, . 2712 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2713 Support for IP Hosts with Multi-Access Support", RFC 7847, 2714 DOI 10.17487/RFC7847, May 2016, 2715 . 2717 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2718 Writing an IANA Considerations Section in RFCs", BCP 26, 2719 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2720 . 2722 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2723 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2724 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2725 July 2018, . 2727 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2728 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2729 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2730 . 2732 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2733 and F. Gont, "IP Fragmentation Considered Fragile", 2734 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2735 . 2737 Appendix A. Interface Attribute Preferences Bitmap Encoding 2739 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 2740 encoding to specific Internetworks such as the Aeronautical 2741 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2742 may include link selection preferences based on other traffic 2743 classifiers (e.g., transport port numbers, etc.) in addition to the 2744 existing DSCP-based preferences. Nodes on specific Internetworks 2745 maintain a map of traffic classifiers to additional P[*] preference 2746 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2747 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2749 Implementations use Simplex or Indexed encoding formats for P[*] 2750 encoding in order to encode a given set of traffic classifiers in the 2751 most efficient way. Some use cases may be more efficiently coded 2752 using Simplex form, while others may be more efficient using Indexed. 2753 Once a format is selected for preparation of a single Interface 2754 Attribute the same format must be used for the entire Interface 2755 Attribute sub-option. Different sub-options may use different 2756 formats. 2758 The following figures show coding examples for various Simplex and 2759 Indexed formats: 2761 0 1 2 3 2762 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2764 | Sub-Type=2| Sub-length=N | ifIndex | ifType | 2765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2766 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 2767 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2768 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2769 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2770 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2771 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2772 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2773 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2774 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2775 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2776 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2777 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2779 Figure 19: Example 1: Dense Simplex Encoding 2781 0 1 2 3 2782 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2783 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2784 | Sub-Type=2| Sub-length=N | ifIndex | ifType | 2785 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2786 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2787 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2788 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2790 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2791 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2792 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2793 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2794 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2795 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2796 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2797 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2798 |Bitmap(10)=0x00| ... 2799 +-+-+-+-+-+-+-+-+-+-+- 2801 Figure 20: Example 2: Sparse Simplex Encoding 2803 0 1 2 3 2804 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2805 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2806 | Sub-Type=2| Sub-length=N | ifIndex | ifType | 2807 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2808 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 2809 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2810 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2811 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2812 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2813 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2814 | Bitmap = 0x01 |796|797|798|799| ... 2815 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2817 Figure 21: Example 3: Indexed Encoding 2819 Appendix B. VDL Mode 2 Considerations 2821 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2822 (VDLM2) that specifies an essential radio frequency data link service 2823 for aircraft and ground stations in worldwide civil aviation air 2824 traffic management. The VDLM2 link type is "multicast capable" 2825 [RFC4861], but with considerable differences from common multicast 2826 links such as Ethernet and IEEE 802.11. 2828 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2829 magnitude less than most modern wireless networking gear. Second, 2830 due to the low available link bandwidth only VDLM2 ground stations 2831 (i.e., and not aircraft) are permitted to send broadcasts, and even 2832 so only as compact layer 2 "beacons". Third, aircraft employ the 2833 services of ground stations by performing unicast RS/RA exchanges 2834 upon receipt of beacons instead of listening for multicast RA 2835 messages and/or sending multicast RS messages. 2837 This beacon-oriented unicast RS/RA approach is necessary to conserve 2838 the already-scarce available link bandwidth. Moreover, since the 2839 numbers of beaconing ground stations operating within a given spatial 2840 range must be kept as sparse as possible, it would not be feasible to 2841 have different classes of ground stations within the same region 2842 observing different protocols. It is therefore highly desirable that 2843 all ground stations observe a common language of RS/RA as specified 2844 in this document. 2846 Note that links of this nature may benefit from compression 2847 techniques that reduce the bandwidth necessary for conveying the same 2848 amount of data. The IETF lpwan working group is considering possible 2849 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2851 Appendix C. MN / AR Isolation Through L2 Address Mapping 2853 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2854 unicast link-scoped IPv6 destination address. However, IPv6 ND 2855 messaging should be coordinated between the MN and AR only without 2856 invoking other nodes on the *NET. This implies that MN / AR control 2857 messaging should be isolated and not overheard by other nodes on the 2858 link. 2860 To support MN / AR isolation on some *NET links, ARs can maintain an 2861 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2862 *NETs, this specification reserves one Ethernet unicast address TBD2 2863 (see: Section 20). For non-Ethernet statically-addressed *NETs, 2864 MSADDR is reserved per the assigned numbers authority for the *NET 2865 addressing space. For still other *NETs, MSADDR may be dynamically 2866 discovered through other means, e.g., L2 beacons. 2868 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2869 both multicast and unicast) to MSADDR instead of to an ordinary 2870 unicast or multicast L2 address. In this way, all of the MN's IPv6 2871 ND messages will be received by ARs that are configured to accept 2872 packets destined to MSADDR. Note that multiple ARs on the link could 2873 be configured to accept packets destined to MSADDR, e.g., as a basis 2874 for supporting redundancy. 2876 Therefore, ARs must accept and process packets destined to MSADDR, 2877 while all other devices must not process packets destined to MSADDR. 2878 This model has well-established operational experience in Proxy 2879 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2881 Appendix D. Change Log 2883 << RFC Editor - remove prior to publication >> 2885 Differences from draft-templin-6man-omni-interface-35 to draft- 2886 templin-6man-omni-interface-36: 2888 o Major clarifications on aspects such as "hard/soft" PTB error 2889 messages 2891 o Made generic so that either IP protocol version (IPv4 or IPv6) can 2892 be used in the data plane. 2894 Differences from draft-templin-6man-omni-interface-31 to draft- 2895 templin-6man-omni-interface-32: 2897 o MTU 2898 o Support for multi-hop ANETS such as ISATAP. 2900 Differences from draft-templin-6man-omni-interface-29 to draft- 2901 templin-6man-omni-interface-30: 2903 o Moved link-layer addressing information into the OMNI option on a 2904 per-ifIndex basis 2906 o Renamed "ifIndex-tuple" to "Interface Attributes" 2908 Differences from draft-templin-6man-omni-interface-27 to draft- 2909 templin-6man-omni-interface-28: 2911 o Updates based on implementation experience. 2913 Differences from draft-templin-6man-omni-interface-25 to draft- 2914 templin-6man-omni-interface-26: 2916 o Further clarification on "aggregate" RA messages. 2918 o Expanded Security Considerations to discuss expectations for 2919 security in the Mobility Service. 2921 Differences from draft-templin-6man-omni-interface-20 to draft- 2922 templin-6man-omni-interface-21: 2924 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2925 (PBM). 2927 Differences from draft-templin-6man-omni-interface-18 to draft- 2928 templin-6man-omni-interface-19: 2930 o SEND/CGA. 2932 Differences from draft-templin-6man-omni-interface-17 to draft- 2933 templin-6man-omni-interface-18: 2935 o Teredo 2937 Differences from draft-templin-6man-omni-interface-14 to draft- 2938 templin-6man-omni-interface-15: 2940 o Prefix length discussions removed. 2942 Differences from draft-templin-6man-omni-interface-12 to draft- 2943 templin-6man-omni-interface-13: 2945 o Teredo 2946 Differences from draft-templin-6man-omni-interface-11 to draft- 2947 templin-6man-omni-interface-12: 2949 o Major simplifications and clarifications on MTU and fragmentation. 2951 o Document now updates RFC4443 and RFC8201. 2953 Differences from draft-templin-6man-omni-interface-10 to draft- 2954 templin-6man-omni-interface-11: 2956 o Removed /64 assumption, resulting in new OMNI address format. 2958 Differences from draft-templin-6man-omni-interface-07 to draft- 2959 templin-6man-omni-interface-08: 2961 o OMNI MNs in the open Internet 2963 Differences from draft-templin-6man-omni-interface-06 to draft- 2964 templin-6man-omni-interface-07: 2966 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2967 L2 addressing. 2969 o Expanded "Transition Considerations". 2971 Differences from draft-templin-6man-omni-interface-05 to draft- 2972 templin-6man-omni-interface-06: 2974 o Brought back OMNI option "R" flag, and discussed its use. 2976 Differences from draft-templin-6man-omni-interface-04 to draft- 2977 templin-6man-omni-interface-05: 2979 o Transition considerations, and overhaul of RS/RA addressing with 2980 the inclusion of MSE addresses within the OMNI option instead of 2981 as RS/RA addresses (developed under FAA SE2025 contract number 2982 DTFAWA-15-D-00030). 2984 Differences from draft-templin-6man-omni-interface-02 to draft- 2985 templin-6man-omni-interface-03: 2987 o Added "advisory PTB messages" under FAA SE2025 contract number 2988 DTFAWA-15-D-00030. 2990 Differences from draft-templin-6man-omni-interface-01 to draft- 2991 templin-6man-omni-interface-02: 2993 o Removed "Primary" flag and supporting text. 2995 o Clarified that "Router Lifetime" applies to each ANET interface 2996 independently, and that the union of all ANET interface Router 2997 Lifetimes determines MSE lifetime. 2999 Differences from draft-templin-6man-omni-interface-00 to draft- 3000 templin-6man-omni-interface-01: 3002 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 3003 for future use (most likely as "pseudo-multicast"). 3005 o Non-normative discussion of alternate OMNI LLA construction form 3006 made possible if the 64-bit assumption were relaxed. 3008 First draft version (draft-templin-atn-aero-interface-00): 3010 o Draft based on consensus decision of ICAO Working Group I Mobility 3011 Subgroup March 22, 2019. 3013 Authors' Addresses 3015 Fred L. Templin (editor) 3016 The Boeing Company 3017 P.O. Box 3707 3018 Seattle, WA 98124 3019 USA 3021 Email: fltemplin@acm.org 3023 Tony Whyman 3024 MWA Ltd c/o Inmarsat Global Ltd 3025 99 City Road 3026 London EC1Y 1AX 3027 England 3029 Email: tony.whyman@mccallumwhyman.com